WATER DISPERSIBLE TABLETS

COMPRIMES DISPERSABLES DANS L'EAU

English Abstract

A water-dispersible tablet comprises: 2% w/w to 90% w/w
lamotrigine or a pharmaceutically acceptable salt thereof, and
0.25 to 40% w/w of a pharmaceutically acceptable swellable
clay which is present within the granules of the tablet to
provide a tablet which is capable of dispersing in water
within a period of 3 minutes to provide a dispersion which is
capable of passing through a sieve screen with a mesh aperture
of 710 µm in accordance with the test for dispersible tablets
defined in the British Pharmacopoeia 1988, Volume II, page
895.

Claims

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CLAIMS
1. A water-dispersible tablet comprising:
2% w/w to 90% w/w lamotrigine or a pharmaceutically
acceptable salt thereof, and
0.25 to 40% w/w of a pharmaceutically acceptable
swellable clay which is present within the granules of the
tablet to provide a tablet which is capable of dispersing in
water within a period of 3 minutes to provide a dispersion
which is capable of passing through a sieve screen with a mesh
aperture of 710 µm in accordance with the test for dispersible
tablets defined in the British Pharmacopoeia 1988, Volume II,
page 895.
2. A tablet as claimed in claim 1, wherein the
swellable clay is a smectite or attapulgite.
3. A tablet as claimed in claim 2, wherein the smectite
is selected from the montmorillonoid group.
4. A tablet as claimed in claim 3, wherein the
montmorillonoid group is selected from the group consisting of
montmorillonite, seuconite, vermiculite, bentonite, hectorite
and magnesium aluminium silicate.
5. A tablet as claimed in claim 4, wherein the
montmorillonoid is magnesium aluminium silicate or bentonite.
6. A tablet as claimed in claim 5, wherein the
magnesium aluminium silicate is Veegum F.
7. A tablet as claimed in any one of the claims 1 to 6,
wherein the swelling clay is present within the granules of
the tablet in an amount of 1 to 40% w/w.


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8. A tablet as claim 7, wherein the swellable clay is
present in an amount of 1 to 10% w/w.
9. A tablet as claimed in claim 8, wherein the
swellable clay is present in an amount of 5 to 10% w/w.
10. A tablet as claimed in any one of claims 1 to 9,
which further comprises a disintegrating agent.
11. A tablet as claimed in claim 10, wherein said
disintegrating agent is sodium starch glycollate or
lowhydroxypropylcellulose.
12. A tablet as claimed in any one of claims 1 to 11,
which further comprises a binder.
13. A tablet as claimed in claim 12, wherein the binder
is povidone k30.
14. A tablet as claimed in any one of claims 1 to 13,
which further comprises a filler.
15. A tablet as claimed in any one of claims 1 to 14,
which is capable of dispersing in water within a period of 2
minutes.
16. A tablet as claimed in any one of claims 1 to 15,
wherein the amount of lamotrigine is 5 to 250 mg.
17. A tablet as claimed in any one of claims 1 to 16,
wherein the dispersion contains particles having a particle
size distribution of 100% less than 710 µm, and more than 50%
less than 300 µm.


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18. A tablet as claimed in claim 17, wherein the
dispersion contains particles having a particle size
distribution of 100% less than 710 µm, more than 70% less than
300 µm, and more than 50% less than 200 µm.
19. A tablet as claimed in any one of claims 1 to 18 ,
wherein the tablet contains 25 to 200 mg lamotrigine or a salt
thereof and comprises a formulation of 30% w/w to 50% w/w
lamotrigine or a salt thereof, 26% w/w to 46% w/w calcium
carbonate, 5 to 30% w/w lowhydroxypropylcellulose-LH11 or
microcrystalline cellulose, 0.25% w/w to 30% w/w magnesium
aluminium silicate or bentonite, 0.25 to 5% w/w povidone or 1
to 8% w/w pregelled starch, 0 to 8% w/w sodium starch
glycollate and 0.25% w/w to 2% w/w magnesium stearate.
20. A tablet as claimed in claim 19, further including a
film coating composite of 0.1% w/w to 2% w/w opadry and 0.1%
w/w to 0.5% w/w polyethylene glycol.
21. A tablet as claimed in claim 19, wherein the
formulation is 35% w/w to 45% w/w lamotrigine or a salt
thereof, 31% w/w to 41% w/w calcium carbonate, 5 to 15% w/w
lowhydroxypropylcellulose or microcrystalline cellulose, 0.25%
w/w to 10% w/w magnesium aluminium silicate or bentonite, 0.5
to 2% w/w povidone or 2 to 5% w/w pregelled starch, 0 to 5%
w/w sodium starch glycollate and 0.25% w/w to 1% w/w magnesium
stearate.
22. A tablet as claimed in claim 21, further including a
film coating composite of 0.25% w/w to 1% w/w opadry and 0.1%
w/w to 0.2% w/w polyethylene glycol.
23. A tablet as claimed in any one of claims 1 to 17,
wherein the tablet contains 5 mg to 50 mg lamotrigine or a


-56-
salt thereof and the formulation comprises 3% w/w to 13% w/w
lamotrigine or a salt thereof, 50% w/w to 60% w/w lactose or
calcium carbonate, 20% w/w to 35% w/w
lowhydroxypropylcellulose or microcrystalline cellulose, 0 to
8% w/w sodium starch glycollate, 0.25% w/w povidone or
magnesium aluminium silicate or bentonite, 0.25% w/w to 5% w/w
povidone or 1% w/w to 8% w/w pregelled starch, 0 to 5% w/w
sodium docusate, 0 to 3% sodium saccharine and 0.25% w/w to 2%
w/w magnesium stearate.
24. A tablet as claimed in claim 23, further including a
film coating composite of 0.1% w/w to 2% w/w opadry, and 0.1%
w/w to 0.5% w/w polyethylene glycol.
25. A tablet as claimed in claim 23, wherein the
formulation is 5% w/w to 11% w/w lamotrigine or a salt
thereof, 53% w/w to 59% w/w lactose or calcium carbonate , 24%
w/w to 30% w/w lowhydroxypropylcellulose or microcrystalline
cellulose, 0 to 5% w/w sodium starch glycollate, 0.25% w/w to
10% w/w magnesium aluminium silicate or bentonite, 0.5% w/w to
2% w/w povidone or 2% w/w to 5% w/w pregelled starch, 0.15%
w/w to 0.5% w/w sodium docusate, 0.5% w/w to 2% sodium
saccharine and 0.25% w/w to 1% w/w magnesium stearate.
26. A tablet as claimed in claim 25, further including a
film coating composite of 0.25% w/w to 1% w/w opadry, and 0.1%
w/w to 0.2% w/w polyethylene glycol.
27. A tablet as claimed in any one of claims 1 to 26,
comprising lamotrigine.
28. A tablet as claimed in any one of claims 1 to 26,
comprising a pharmaceutically acceptable salt of lamotrigine.


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29. A tablet according to any one of claims 1 to 28,
wherein said tablet is capable of:
a) dispersing in water to provide a dispersion which
passes through a sieve screen with a mesh aperture of 710 µm;
b) disintegrating within three minutes when examined by
the following apparatus and method in accordance with the test
for dispersible tablets of the British Pharmacopoeia, 1988,
Volume II, page: 895; said apparatus consisting of:
(i) a rigid basket-rack assembly supporting six
cylindrical glass tubes 75.0 to 80.0 mm long, 21.5 mm in
internal diameter and with a wall thickness of about 2 mm;
(ii) a cylindrical disc for each tube, each 20.55 to
20.85 mm in diameter and 9.35 to 9.65 mm thick, made of
transparent plastic with a relative density of 1.18 to 1.20,
pierced with five holes, each 2 mm in diameter, one in the
center and the other four spaced equally on a circle of radius
6 mm from the center of the disc, there being four equally
spaced grooves cut in the lateral surface of the disc in such
a way that at the upper surface of the disc they are 9.5 mm
wide and 2.55 mm deep and at the lower surface 1.6 mm square;
(iii) two superimposed transparent plastic plates 90
mm in diameter and 6 mm thick, perforated by six holes having
the same diameter as the tubes and holding the tubes
vertically, the holes being equidistant from the center of the
plate and equally spaced from one another, and a piece of
woven gauze made from stainless steel wire 0.635 mm in
diameter and hawing nominal mesh apertures of 2.00 mm attached
to the underside of the lower plate;
(iv) said plastic plates being held rigidly in
position and 77.5 mm apart by vertical metal rods at the
periphery and a metal rod fixed to the center of the upper
plate to enable the assembly to be attached to a mechanical
device capable of raising and lowering it smoothly through a


-58-
distance of 50 to 60 mm at a constant frequency of between 28
and 32 cycles per minutes;
(v) said assembly being suspended in water at 19° to
21°C. held in a 1000 ml beaker, the volume of water being such
that when the assembly is in the highest position the wire
mesh is at least 15 mm below the surface of the water and when
the assembly is in the lowest position the wire mesh is at
least 25 mm above the bottom of the beaker and the upper open
ends of the tubes remain above the surface of the water; said
method consisting of introducing one tablet into each of the
six tubes, suspending said assembly in the beaker containing
the water and operating the apparatus for a maximum period of
three minutes so that all six of the tables disperse.
30. A process for the preparation of a water-dispersible
tablet or a pharmaceutically acceptable salt comprising 2% to
90% w/w lamotrigine or a pharmaceutically acceptable salt
thereof and 0.25 to 40% w/w of a pharmaceutically acceptable
swellable clay; said process comprising bringing lamotrigine
into association with said swellable clay to form granules,
and then compressing the granules to form a tablet which is
capable of dispersing in water within a period of 3 minutes to
provide a dispersion which is capable of passing through a
sieve screen with a mesh aperture of 710 µm in accordance with
the test for dispersible tablets defined in the British
Pharmacopoeia, 1988, Volume II, page 895.
31. A process according to claim 30, wherein said tablet is
capable of:
a) dispersing in water to provide a dispersion which
passes through a sieve screen with a mesh aperture of 710 µm;
b) disintegrating within three minutes when examined by
the following apparatus and method in accordance with the test


-59-
for dispersible tablets of the British Pharmacopoeia, 1988,
Volume II, page: 895; said apparatus consisting of:
(i) a rigid basket-rack assembly supporting six
cylindrical glass tubes 75.0 to 80.0 mm long, 21.5 mm in
internal diameter and with a wall thickness of about 2 mm;
(ii) a cylindrical disc for each tube, each 20.55 to
20.85 mm in diameter and 9.35 to 9.65 mm thick, made of
transparent plastic with a relative density of 1.18 to 1.20,
pierced with five holes, each 2 mm in diameter, one in the
center and the other four spaced equally on a circle of radius
6 mm from the center of the disc, there being four equally
spaced grooves cut in the lateral surface of the disc in such
a way that at the upper surface of the disc they are 9.5 mm
wide and 2.55 mm deep and at the lower surface 1.6 mm square;
(iii) two superimposed transparent plastic plates 90
mm in diameter and 6 mm thick, perforated by six holes having
the same diameter as the tubes and holding the tubes
vertically, the holes being equidistant from the center of the
plate and equally spaced from one another, and a piece of
woven gauze made from stainless steel wire 0.635 mm in
diameter and having nominal mesh apertures of 2.00 mm attached
to the underside of the lower plate;
(iv) said plastic plates being held rigidly in
position and 77.5 mm apart by vertical metal rods at the
periphery and a metal rod fixed to the center of the upper
plate to enable the assembly to be attached to a mechanical
device capable of raising and lowering it smoothly through a
distance of 50 to 60 mm at a constant frequency of between 28
and 32 cycles per minutes;
(v) said assembly being suspended in water at 19° to
21°C. held in a 1000 ml beaker, the volume of water being such
that when the assembly is in the highest position the wire
mesh is at least 15 mm below the surface of the water and when
the assembly is in the lowest position the wire mesh is at


-60-
least 25 mm above the bottom of the beaker and the upper open
ends of the tubes remain above the surface of the water; said
method consisting of introducing one tablet into each of the
six tubes, suspending said assembly in the beaker containing
the water and operating the apparatus for a maximum period of
three minutes so that all six of the tables disperse.

Description

CA 02277722 2000-08-02
The present invention relates to a water-dispersible tablet
formulation containing a therapeutically active compound.
his Apps ; ~~; ~ is a Divi~irnal of Canadian Patent Application, S-N-
2,098,108, filed Januazy 2!~, 1992.
Therapeutically active compounds or drugs are frequently administered
to patients. in tablet farm where the drug is intended for oral
administration since tablets are an :especially convenient
pharmaceutical form for manufacture, storage .and generally usage.
However, problems., may arise with tre administration of such tablets
to patients who have d~.fficulty in swallowing the tablets (for
example, children or morE: seriously ill patients),especially if the
tablets are large in size arising from the amount of drug required in
each tablet. A solution ~:o such problems is to formulate the tablets
in a form whereby they can be dispersed in water to form a dispersion
containing the dnig which can then be drunk by the patient.
Known water-dispa_rsible tablets include effervescent formulations
which rely on the formation of a gas to quickly break up the tablet,
but these involve expensive methods of manufacture and strict
regulations for such manufacture. Other known water-dispersible
tablets use disintegratin~~ agents such as microcrystalline cellulose
used in Feldene ;Et dispezsible tablets. We have tested well-known
disintegrating agents (in~:orporated both.internally and externally to
the preformed granules) such as sodium starch glycollate (e. g.
Explotab), cross-linked p widone (e. g. Kollidon CL) and a cross-linked
sodium carboxymethylcell~~lose (e.g. Starch, Avicel PH102, and
Ac-Di-Sol) in an acyclovir tablet, but found that they did not provide
a satisfactory water-dispersible formulation. We furthermore' tested
an ion exchange resin (Amberlite 1RP88) as a disintegrating agent and
incorporated surface active agents (e.g. sodium lauryl sulphate and
sodium docusate) in an attempt to improve tablet wetting and
penetrating of water during dispersion, but in all cases the
disintegration time was high.
Explotab, Rollidon, Avicel, Ac-Di-Sol and Amberlite are Trade-
marks-


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163 ,
_ 2 _
After considerable research and investigation, we have now suprisingly
found that the use of a swellable clay within the granulate of a
tablet formulation provides a tablet which has good dispersibility in
water to provide a dispersion which can be drunk by a patient.
Swellable clays such as VeegumR and other magnesium aluminium
silicates have previously been studied and proposed for use as
disintegrating agents, binders and lubricants in the manufacture of
tablets, but such studies and proposals were exclusively with respect
to tablets intended for swallowing and not for water-dispersible
tablets (Rubenstein, Pharmaceutics - The Science of Dosage Form Design
(1990) for disintegrants see p 312 and 314), Moreover, there has -_
never been any su;~gestion that a clay would be suitable to meet the
more stringent r~squirements for dispersible tablets. Tablets for
swallowing need only have a disintegration time in water of less 15
minutes and be able to form particles on disintegration in water that
can pass through a 2.OOmm mesh aperture (British Pharmacopia test for
swallowable tablets). Such long disintegration times and large
particle sizes arE: entirely unsuitable for a dispersible tablet.
Even when swellab:Le clays have been proposed as disintegrating agents
for swallowable tablets, they are not regarded as very suitable for
such use because their off-white appearance can often discolour the
tablet and becausE: they are not as effective as other disintegrating
agents (Banker and Anderson - Theory and Practice of Industrial
Pharmacy p 328 1;1986) and Bhargava et a~ - Drug Development and
Industrial Pharmacy, 17(:L5), 2093-2102(1991)). In fact, bentonite is
identified in Mar:;hall and Rudnic, Modern Pharmaceutics (1990) p 374,
as the least swell.able of the ten disintegrants listed. There is no
mention in the above text-book references of how the swellable clay
should be incorporated - i.e. by intra-granular addition or by
extra-granular addition. In the former case, the clay would be
included in the mixture from which the granulate is formed; in the
latter case the clay would be added to the pre-formed granulate.

:w.~
CA 02277722 1999-08-OS
WO 92/13527 PCf/GB92/00163
- 3 -
In J. Pharm. Sci, 55, 1244 (1966), Wai et ~1, reviewed the following
papers relating to swellable clays such as Veegum and bentonite as
disintegrating agents: Wai et a~., J.Pharm.Sci, 55, 1215(1966);
Granberg et al., J.Am.Pharm.Assoc.Sci, 38, 648(1949); Gross et al.,
J.Am.Pharm.Assoc.:~ci, 41, 157(1952); Firouzabadian et al.,
J.Am.Pharm.Assoc.Sci, 43, 248(1954); Ward et al., Drug Cosmetic Ind,
91, 35(1962); Nair et a_~,., J.Am.Pharm.Assoc.Sci, 46, 131(1957); and
Patel et a~., Indian J.Pharm., 19, Jan.1957. Wai et al., then compared
three grades of: Veegum evalulating both extra-granular and
intra-granular addition and concluded that "the clays were not good
disintegrating a~;ents when wet granulated" (i.e. intra-granular
addition), and then went on to recommend extra-granular addition.
Furthermore R.T.Vanderbilt and Co. (Manufacturers of Veegum) in their
publication "Veegum - 'The Versatile Ingredient for Pharmaceutical
Formulations" at F~ 19 describe a tablet formulation in which Veegum is
added after granulation (tablet No.2). There is no reference in the
publication to a formulation of a tablet in Which Veegum is added
during granulation.
In contrast to t:he above recommendations, we have found that a
swellable clay such as Veegum must be added during granulation to meet
the British Phannacopoeia (B. P.) standard for dispersible tablets
(presently set at a dispersion time of 3 minutes or less). If the
swellable clay is added only after granulation the dispersion time is
too high to meet the above standard.
By using Veegum and other swellable clays in the manner described
above, we have been able to prepare water-dispersible tablets
containing a variety of therapeutically active compounds. The
resulting tablets can readily be dispersed in water to form a
dispersion which can be drunk by a patient.
According to the present invention there is provided a water-dispersi-
ble tablet comprising a therapeutically active compound selected from
the group consisting of an analgesic propionic acid derivative, a


CA 02277722 1999-08-OS
- 4 -
tranquillising benzodiazepine, an anti-viral nucleoside
derivative (f~~r example acyclovir), an anti-protozoal
naphthoquinone, allopurinol, oxopurinol, anti-convulsant 1,2,4
triazine derivative (for example lamotrigine) and trimethoprim
(optionally in combination with sulphamethoxazole), together
with an effective amount of a pharmaceutically acceptable
swellable clay to provide a tablet which is capable of
dispersing in water within a period of 3 minutes to provide a
dispersion which is capable of passing through a sieve screen
with a mesh aperture of 710 ~tm in accordance with the test for
dispersible tablets defined in the British Pharmacopoeia,
1988, Volume II, page 895.
The afore-mentioned published test requires that the tablet be
capable of a) dispensing in water to provide a dispersion
which passes through a sieve screen with a mesh aperture of
710 ~,m; b) disintegrating within three minutes when examined
by the following apparatus and method in accordance with the
test for dispersible tablets of the British Pharmacopoeia,
1988, Volume II, page 895; said apparatus consisting of: (I) a
rigid basket-rack assembly supporting six cylindrical glass
tubes 75.0 to E30.0 mm long, 21.5 mm in internal diameter and
with a wall thickness. of about 2 mm; (ii) a cylindrical disc
for each tube, each 20.55 to 20.85 mm in diameter and 9.35 to
9.65'mm thick, made of transparent plastic with a relative
density of 1.18 to 1.20, pierced with five holes, each 2 mm in
diameter, one in the center and the other four spaced equally
on a circle of radius 6 mm from the center of the disc, there
being four equally spaced grooves cut in the lateral surface
of the disc in such a way that at the upper surface of the
disc they are ~~.5 mm wide and 2.55 mm deep and at the lower
surface 1.6 mm square


CA 02277722 1999-08-OS
- 4a -
(iii) two superimposed transparent plastic plates 90 mm in
diameter and 6 mm thick, perforated by six holes having the
same diameter a.s the tubes and holding the tubes vertically,
the holes being equidistant from the center of the plate and
equally spaced from one another, and a piece of woven gauze
made from stain:Less steel wire 0.635 mm in diameter and having
nominal mesh apertures of 2.00 mm attached to the underside of
the lower plate; (iv) said plastic plates being held rigidly
in position and. 77.5 mm apart by vertical metal rods at the
periphery and a metal rod fixed to the center of the upper
plate to enable: the assembly to be attached to a mechanical
device capable of raising and lowering it smoothly through a
distance of 50 to 60 mm at a constant frequency of between 28
and 32 cycles per minutes; (v) said assembly being suspended
in water at 19° to 21"C. held in a 1000 ml beaker, the volume
of water being such that when the assembly is in the highest
position the wire mesh is at least 15 mm below the surface of
the water and when the assembly is in the lowest position the
wire mesh is at least 25 mm above the bottom of the beaker and
the upper open ends of the tubes remain above the surface of
the water; said method consisting of introducing one tablet
into each of the six tubes, suspending said assembly in the
beaker containing the water and operating the apparatus for a
maximum period of three minutes so that all six of the tables
disperse.


CA 02277722 1999-08-OS
- 4b -
The above-defined therapeutically active compound employed in
the tablet according to the invention is hereinafter referred
to as "the active compound".
The present inventic>n further provides a process for the
preparation of: a water-dispersible tablet comprising a
therapeutically active compound selected from the group
consisting of an analgesic propionic acid derivative, a
tranquillising benzodiazepine, an anti-viral nucleoside
derivative, an anti-protozoal naphthoquinone, allopurinol
oxopurinol, anti-convulsant 1,2,4 triazine derivative and _
trimethoprim (opt:ionally in combination with
sulphamethoxazole), together with an effective amount of a
pharmaceutically acceptable swellable clay which comprises
bringing the said active compound into association with the
said swellable clay to provide a water-dispersible.table which
is capable of d.ispers.ing in water within a period of 3 minutes
to provide a dispersion which is capable of passing through a
sieve screen with a mesh aperture of 710 ~m in accordance with
the test for dispei:sible tablets defined in the British
Pharmacopoeia, 1988, ~lolume II, page 895.
Preferably said process comprises the steps of:


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- S -
a) admixing in dry, finely-divided form the active compound with an
effective amount o.f a pharmaceutically acceptable swellable clay,
optionally with the addition of one or more other pharmaceutical
carriers or excipients;
b) addition of a quantity of a pharmaceutically acceptable liquid
sufficient t:o moisten the dry mixture;
c) granulation of the resulting moist mixture to form granules;
d) drying the granules and optionally blending the granules with
other optional carriers or excipients such as lubricants,
glidants, flavouring agents and disintegrating agents; and
e) compression of the granules to form a tablet which is capable of
dispersing i.n water within a period of 3 minutes to provide a
dispersion ~rhich is capable of passing through a sieve screen
with a mesh aperture of 710~m in accordance with the above
defined British Pharmacopoeia test for dispersible tablets.
A tablet according to the invention, as well as being quickly
dispersible in water, has the added advantage that it meets the
British Pharmacopoeia (B. P.) test for dispersible tablets in respect
of dispersion times and dispersion quality (i.e. passage through a
710um sieve).
Preferably the dispersion time of a tablet according to the invention
is less than 2 minutes, more preferably less than 1.50 minutes and
_ most preferably less than 1 minute.
A further advantage of the tablets according to invention is that
because a relati~~ely fine dispersion is formed.the tablet will have a
lower dissolution time and thus the drug may be absorbed into the
blood stream much faster. Furthermore the fast dispersion times and
relatively fine dispersions obtained with tablets according to the


CA 02277722 1999-08-OS
~%O 92/13527 PCT/GB92/00163
- 6 -
invention are also advantageous for swallowable tablets. Thus tablets-
according to the invention can be presented both for dispersion in
water and also for directly swallowing. Those tablets according to
the invention that are intended for swelling are preferably
film-coated to aid swallowing. Such film-coating however increases
the dispersion time up to 5 minutes determined in accordance with the
above-mentioned B.P. test.
According to a further feature of the present invention therefore we
provide a water-dispersible film-coated tablet comprising a
therapeutically active compound selected from the group consisting of
an analgesic propionic acid derivative, a tranquillising
benzodiazepine, as antiviral nucleoside derivative, an anti-protozoal
napthoquinone, allopurinol, oxopurinol, an anti-convulsant
1,2,4-triazine derivative and trimethoprim (optionally in combination
with sulphamethoxazole), together with an effective amount of a
pharmaceutically acceptable swellable clay to provide a film-coated
tablet which is capable of dispersing in Water within a period of 5
minutes to provide a dispersion which is capable of passing through a
sieve screen with a mesh aperture of 710~m in accordance with the
above-defined British Pharmacopoeia test for dispersible tablets
subject to the variation of the said period specified in the test from
3 minutes to S minutes. The references herein to tablets according to
the invention include bath film-coated and non-film-coated tablets.
After the dispersion has passed through the 710~cm mesh screen, there
should be substantially no residue, except fragments of undissolved
tablet coating or shell, remaining on the screen or adhering to the
lower surface of the disc, if a disc optionally has been used; and if
any residue remains, it: should consist of a soft mass having no
palpably firm, unmoistened core.
The particle size distribution of the dispersion particularly when the
active compound is acyclovir are set out in the following table with
the increasingly preferred values being quoted from left to right.

CA 02277722 2000-08-02
- 7 -
Particle BP More Most
Size (~m)* Standard Preferably Preferably Preferably
<710 <100% 100% 100% 100%
<300 - >50% >70% >80%
<200 - - >50% >70%
<150 - - - >50%
* (equivalent spherical volume diameter)
Examples of active compounds which have been employed in the tablets
according to the invention are listed below together with respective
patent publications, (in s~ppropriate instances) which teach how to
make them and infecaions ot~ medical conditions which can be treated by
them acyclovir (UR Nu= 1523865), Lamotrigine
-(EP Nos: 021 1.21 and 247 829) diazepam, paracetamol, -
(both commercially available), 1-(~-D-arabinofuranosyl)-5-propy-1-
ynyl-uracil (EP No. 0272 065), 2-[4-(4-chlorophenyl)cyclohexylJ-3-
hydroxy- 1,4-naphthoquinone: (EP No. 0123 238), allopurinol (G.B. No.
1445 983).
Examples of other active compounds include: 3'-azido-3'-deoxythymidine
(EP No. 0196 185), S-prop-1.-ynyl-1-(5-trimethylacetyl-~-D-arabinofura-
nosyl)uracil (EP No. 0375 7.64), 2-(2-amino-1,6-dihydro-6-oxo-9H(purin-
9-yl)methoxy)ethyl-valinatE: (EP No. 0308 065), 2',3'-dideoxy-5-ethyn- ..
yl-3'-fluorouridine (EP No. 0356 166), 5-chloro-1-(2,3-dideoxy-3-fluo-
ro-~-erythropeatofuranosyl;uracil (EP No. 0305 117 and EP No. 0317
128), penciclovir, i.e. 9-[4-hydroxy-3-(hydroxymethyl)butylJguanine
(EP No. 141927), famciclovi.r, i.e. 2-amino-9-[4-acetoxy-3-(acetoxyme-
thyl)butylJ purine (EP No. 0182024) and E-5-(2-bromovinyl)-1-~-arabi-
nofuranosyluracil ~; EP No. (1031 128), dextromethorphan, pseudophedrine,
acrivastine, triprolidine, guaiphenesine, dihydrocodeine, codeine
phosphate and ascorbic acid.


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
_ g _
Preferably the active compound is lamotrigine, i.e.(3,5-diamino-6-
(2,3-dichlorophenyl)-1,2,4-triazine, more preferably acyclovir or
pharmaceutically acceptable salts of these compounds which have
acceptable dispersibilit:y in water. Thus, for example, a suitable
salt of lamotrigine is the isethionate salt (i.e. 2-hydroxymethanesul-
phonate).
It will be appreciated that reference to any active compound also
includes any pha=maceuti.cally acceptable salts thereof.
The term "swellable clay" as used herein includes layered clays (such
as smectites), porous fibrous clay minerals, and synthetic clay '_
materials related. in structure to layered clays and porous fibrous
clays.
The term "layered clays" as used herein includes substantially
homogeneous layered~clays and mixtures thereof, and interstratified or
mixed layered clays. Substantially homogeneous layered clays includes
the smectite group for example dioctahedral and trioctahedral types.
Examples of dioctahedral smectites are .the montmorillonite group
(montmorillonoids); magnesium and other (e. g. calcium) aluminium
silicates such as Veegum in its various grades e.g. Veegum, Veegum HV,
Veegum F, and Veegum W'G); almasilate; fullers earth (e. g. Surrey
finest); American fullers earth; bentoni.te; beidellite; cheto
montmorillonite, Wyoming montmorillonite, Utah montmorillonite;
Tatalia and Chambers montm:orillonites; and iron rich smectites such as
nontrite (e. g. Garfield nontronite) and ferrian smectites.
Examples of triocatahedral smectites (also known as saponites) are
Swinefordite, hectorite, stevensite. Examples of smectites containing
more unusual elements are Volkhonsite, Medmontite, Sauconite, nickel
smectites and vanadium smectites. As well as the monimiorillonite
group, related smectites such as vermiculites may also have
application.


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- 9 -
The term "interstratified or mixed layer clays", as used herein
includes clays involving different layers arranged in a regular or
irregular structure. The most common examples of such clays have
generally two comyponents in substantially equal proportions and have
been given mineral names such as rectorite (mica-smectite),
hydrobiotite (bi~tite-vermiculite), corrensiten (chlorite-smectite)
allettite (talc-saponite). More irregular arrangements include
illite-smectite, chlorite-smectite, and kaolinite-smectite. Further
examples of interstratified clays are tosudite, tarasovite,
allevardite, Japanese bentonite ("acid clays"), AWAZU acid clay, and
kaolinite-smectite. Other mixed layer clays may include one or more
of the following minerals: clinchlore, chamosite, nimite, thuringite, -_
sudoite, and~cookeite. Mixed layer smectities are also known e.g.
interdispersed montmorillonite and beidellite layers. The layers of
mixed layer clays may be homogeneous or non-homogeneous.
The term "porous fibrous clays" includes palygorskite and sepiolite
such as, for example attapulgite and American fuller's earth.
The term "synthetic clay materials" as used herein includes materials
related in structure to layered clays and porous fibrous clays such as
synthetic hectorite (lithium magnesium sodium silicate) for example
laponite R.
It will be appreciated that within the scope of the invention the
following classes of clays have application alone or in combination
and in mixed layer clays: kaolinites, serpentines, pyrophyllites,
talc, micas and brittle micas, chlorites, smectites and vermiculites,
palygorskites and. sepiolites. Other phyllosilicates (clay minerals)
which may be employed i.n the tablets according to the invention are
allophane and imogolite.
The following references describe the characterisation of clays of the
above types: Chemistry of Clay and Clay Minerals. Edited by A.C.D.
Newman. Mineralogical Society Monograph No. 6, 1987, Chapter 1; S.W.


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- 10 -
Bailey; Summary of recommendations of AIPEA Nomenclature Committee,
Clay Minerals 15, 85-93; and A Handbook of Determinative Methods in
Mineralogy, 1987, Chapter 1 by P.L. Hall.
Suitably the swellable: clay is a pharmaceutically acceptable
crystalline mineral clay having a lattice structure which expands upon
hydration, preferably a pharmaceutically acceptable smectite or
attapulgite clay, especially a montmorillonoid, more preferably yet a
montmorillonoid chosen from the group consisting of montmorillonite,
sauconite, vermiculite, bentonite and hectorite, still more preferably
an aluminium ma esium silicate and most R
gn preferably Veegum .
The term "smectite" as used herein in relation to tablets of the
present invention includes the smectites as exemplified herein and
with reference to 0'Brian P, and Williamson C.J., in "Clays and Clay
Minerals vol. 38 No. 3 pp322-326, 1990" and the other clay
nomenclature references set out hereinbefore.
The term "magnesium aluminium silicate" as used herein in relation to
tablets of the present invention should be understood to include the
Aluminium Magnesium Silicate defined in the British Pharmacovoeia,
volume I, pages 27-28, 1988 and the Magnesium Aluminium Silicate
defined in the United States Pharmacopoeia, National Formularv XVI',
pages 1943-1944, 1990. Advantageously, said silicate is in the form
of a microfine powder having a No. 325 US Standard mesh particle size,
a viscosity of 250 cps (~ 25%) for a 5.5% (w/v) aqueous dispersion and
an acid demand (the volume in ml. of O.1N hydrochloric acid required
to reduce the pH of one gram to 4) of 6-8: such a material is
available as VEEGUM F (R.T. Vanderbilt Co., New York, N.Y., U.S.A.; K
& K-Greeff Chemicals Ltd., Croydon, Surrey CR9 3QL, England).
The amount of swellable clay employed in the tablet according to the
invention generally depends on the weight of the tablet. Experiments
with acyclovir indicate for a 100mg tablet, amounts as low as 0.25%
w/w of tablet ca.n be used whereas for tablets of about 1000mg to


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1200mg up to 60% w/w, advantageously up to 50% w/w preferably up to
40% w/w could bE~ used to give a satisfactory dispersible tablet in
accordance with t:he invention. Other practical considerations such as
poor flow and cocnpression properties may, however, limit the maximum
percentage weight. of clay which can be incorporated within any given
weight of tablet.. In our experiments up to 40% w/w of swellable clay
was used for a t<iblet having a total weight of Il00mg and gave fine
dispersions and past dispersion times.
Thus for a dispersible tablet containing an active compound defined
hereinbefore such as acyclovir or lamotrigine, the intra-granular
amount of swellable clay such as a crystalline mineral clay for
example, magnesium aluminium silicate is suitably present in the
following genera:L ranges 0.25 to 60% w/w, preferably 0.25 to 50% w/w,
more preferably 0.5 to 50% w/w, more preferably still 1 to 50% w/w,
more preferably ;still 1 to 40% w/w, more preferably still 2 to 20%
w/w, more preferably still 2.5 to 20% w/w, still more preferably 3 to
10% w/w, and most preferably 5 to 10%, most desirably about 5% w/w.
The tablets according to the invention will generally contain a
pre-determined amount of the active compound, depending on the
identity of the compound, the desired dosage and the total weight of
the tablet.
When the active compound is acyclovir, the tablets generally contain
100 to 1000mg, preferably 200 to 800mg, such as 400 to 800mg of the
compound. Such dosage units may be administered one or more times,
for example up to five times, per day, at the discretion of the
physician, according to the age and condition of the patient and the
particular condition being treated. For an acyclovir tablet having a
total weight about 1000 to 1200mg and containing about 750 to 850mg of
acyclovir, the swellable clay e.g. Veegum F, is preferably present in
an amount of 40 to 120 mg it;itragranularly.


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When the active compound is lamotrigine or a pharmaceutically
acceptable salt thereof the tablets according to the invention
conveniently contain 2.5 to 500 mg. desirably 5 to 250 mg. of
lamotrigine calculated as Iamotrigine base. Preferred said unit doses
include 5 mg., 12.5 mg., 25 mg., 50 mg., 100 mg., 150 mg., 200 mg. and
250 mg., calculated as the base. For tablets having a total weight of
about 55 to 65mg and containing about 5mg lamotrigine, the swellable
clay, e.g. Veegu;m F, is preferably present in an amount of 2 to 4mg,
especially about 3mg. Similarly for a tablet having a weight of about
220 to 350mg and containing about 80 to 120mg, preferably 100mg of
lamotrigine, the swellable clay, e.g. Veegum F, is preferably present
in amount of 5 to 20mg, especially about l2mg. -
In general the tablets according to the invention contain the active
compound in the following percentage proportions:-
Acyclovir - 20 to 90% w/w, preferably 45 to 85% w/w
Lamotrigine - 3 to 90% w/w, preferably 5 to 40% w/w
1-(~-D-arabinofuranosyl)-5-propynyl-1-ynyluracil - 10 to 90% w/w,
preferably 65 to 80% w/w
Paracetamol - 50 to 90% w/w, preferably 60 to 75% w/w
2-[4-(4-chlorophenyl)cyclohexylJ-3-hydroxy-1,4-naphthoquinone - 50 to
85% w/w, preferably 60 to 75% w/w
Allopurinol - 25 to 80% w/w, preferably 45 to 65% w/w
Diazepam - 4 to 30% w/w, preferably 8 to 16% w/w
Pseudoephedrine - 5 to 50% w/w, preferably 15 to 30% w/w
Dextromethorphan - 2 to 20% w/w, preferably 5 to 15% w/w


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Triprolidine - 10 to 50% w/w, preferably 20 to 30% w/w
Codeine phosphate
Dihydrocodeine
Ascorbic Acid
Acrivastine - 1 to 10% w/w, preferably 2 to 5% w/w
Guaiphenesine - 10 to 40% w/w, preferably 15 to 30% w/w
Ibuprofen - 20 to 5~0% w/w" preferably 65 to 85% w/w
When the active compound I;such as acyclovir) is present in an amount
of at least 60% wfw in tablets according to the invention, we have
suprisingly found that the dispersion time remains substantially
constant over a range of tablet hardnesses. This is a considerable
quality control advantages since in industrial manufacture it is
essential to maintain a constant tablet hardness. Tablets according
to the invention c:an thus be produced with sufficient hardness and
friability so that they can easily be film-coated. A tablet according
to the invention should desirably have a friability of . about 2% or
less, preferably 0.5% or less.
Based on experiments that we have carried out, it has been found that
in addition to tree amount of swellable clay present within the
granules of the tablet, a further amount of swellable clay may be
present outside the granules. At very low intra-granular amounts
(such as 1% w/w or below), higher extra-granular amounts (such as
about 10% w/w or more) may decrease the dispersion time, but in
general extra-granular addition has little or no effect on the
dispersion time. 7.'he maximum percentages) of the clay present within
the granules and, optionally outside the granules, may be limited by
other practical considerations such as poor flow and compression
properties.


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- 14 -
Other excipients suitable for inclusion in the tablets according to
the invention include the following:
a) Binders and Adhesives: we have found e.g. with acyclovir tablet
formulations that i.f there is sufficient amount of swellable clay
such as Veegum F present within the granules, then a separate
binder is not required (i.e. the clay also acts as a binder).
Preferably however a separate binder is present in a sufficient
amount to provide a tablet having a satisfactory tablet hardness
and satisfactory dispersion characterstics. The amount of binder
will vary depending on the overall tablet formulation and type of
binder used but general functional limits for most tablets of the
invention are 0 to 25% w/w. The following binders and amounts
are suitable for inclusion in a tablet according to the
invention. The concentration. of the binder in the granulation
fluid (% w/v) is given (% w/w in tablet will vary according to
the volume of granulating solution used to form a satisfactory
tablet): Examples of binders are: acacia mucilage 0 to 25% w/v,
preferably 1 to 5% w/v, alginic acid 0 to 20.0% w/v, preferably 1
to 5% w/v, polyvinylpyrrolidone (povidone) 0 to 15.0% w/v,
preferably 0.5 to 5% w/v, gelatin 0 to 20.0% w/v, preferably 1 to
5.0% w/v, su.crose 0 to 70.0% w/v, preferably 2.0 to 20.0% w/v,
starch mucilage 0 to 10.0% w/v, preferably 0.5 to 5.0% w/v,
pregelatinised starch 0 to 10.0% w/v, preferably 0.5 to 5.0% w/v,
starch paste 0 to 10.0% w/v, preferably 5.0 to 10.0% w/v, sodium
alginate 0 t.o 5.0% w/v, preferably 1.0 to 3.0% w/v, sorbitol 0 to
10.0% w/v, preferably 3.0 to 10.0% w/v, tragacanth 0 to 20% w/v,
preferably 5.0 to 1Ø0% w/v, glucose 0 to 50%, preferably 5 to
25% w/v, hydroxypropylmethyl cellulose (HPMC) 0 to 10% w/v,
preferably 1..0 to 5.0% w/v, magnesium aluminium silicate 0 to 40%
w/v, preferably 2 to 10% w/v, starch paste 0 to 25% w/v,
preferably 5 to 15% w/v, polyvinylpyrrolidone 0 to 15% w/v,
preferably 3 to 10% w/v, carboxymethylcellulose sodium 0 to 10%
w/v, prefera.bly 1 to 6% w/v, dextrin 0 to 50% w/v, preferably 5
to 25% w/v, ethyl cellulose 0 to 10% w/v, preferably 1 to 6% w/v,


CA 02277722 2000-08-02
- 15 -
polyethylene glycol 0 to 5% w/v, guar gum 0 to 10% w/v,
preferably 1 t~o 5% w/v, zein 0 to 30% w/v, preferably 1 to 10%
w/v, hydroxyethyl cellulose 0 to 5% w/v, preferably 2 to 4% w/v,
hydroxypropyl cellulos~a up to 5% w/v, preferably 2 to 4% w/v,
methyl cellulose up 'to 20% w/v, preferably 1 to 10% w/v,
polymethacrylates up ~to 25% w/v, preferably 5 to 10% w/v,
carboxymethylcellulose calcium 0 to 20% w/v, preferably 5 to 10%
w/v.
b) Disintegrating agents: Tablets according to the invention can be
formulated in the absence of separate disintegrating agents
although their incl°ision may be advantageous for their -
disintegration in water as an adjunct to the dispersion afforded
by the clay above. E~Kamples of suitable disintegrating agents
Which can optionally be incorporated into a tablet according to
the invention are: microcrystalline cellulose (e.g. Avicel R) 0
to 30% w/w, preferably 5 to 10% w/w, Sodium carboxymethyl
cellulose (e. g. Nymcel R) 0 to 5% w/w, preferably 1 to 2% w/w,
calcium carboxymethyl cellulose 0 to 20% w/w, preferably 1 to 5%
w/w, modified cellulose gWm (e. g. Ac-Di-Sol R) 0 to 10% w/w,
preferably 1 to 5% w/w, cross-linked povidone 0 to 10% w/w, .
preferably 2 to 6% w/w, alginic acid and alginates 0 to 10% w/w,
2 to 5% w/w, pregelatinised starch 0 to 10% w/w, preferably 0.5
to 5% w/w, sodium starch glycollate (e.g. Explotab R, Primojbl R)
0 to 10% w/w, preferably 0.5 to 5% w/w, modified corn starch
(e. g. starch 1500 R) 0 to 20% w/w, preferably 1 to 10% w/w,
starch (e.g. potato/maize starch ) 0 to 15% w/w, preferably 0.2
to 10% w/w, ion exchange resin such as polacrin potassium (e. g.
Amberlite IRP-88) up to 5% w/w, preferably 0.5 to 2.0% w/w. The
"R" following the brand names above indicates a Trade- ,
mark; Amberlite is also a Trade-mark:
Work with lamotrigine and other active compounds is sup-
portive of the view that if LHPC is used a suitable dis-
persion can 'be obtained without the need for a separate
wetting agent/surfactant:


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- 16 -
c) Fillers: These serve the purpose of bulking up the tablet to a
suitable size and aiding compressibility especially in lower
dosage tablets. The amount of filler depends on its type, size
of tablet and amount of active compound. When the concentration
of active compound is below 60% w/w, more preferably 45% w/w and
most preferably below 30% w/w, an inorganic water-insoluble
filler is advantageously used. Examples of Water-soluble fillers
(which can he used in general quantities of 0 to 95% w/w) are:
soluble lactose, compressible sugar, confectioners sugar,
dextrose, m;annitol, sodium chloride, sorbitol, xylitol, sodium
chloride F. Examples of water-insoluble fillers (Which can be
used in general quantities of 0 to 93% w/w) are: calcium
carbonate, magnesium carbonate, calcium phosphate (e.g. di and
tri basic calcium phosphate), calcium sulphate, kaolin,
microcrysta:Lline cellulose, powdered cellulose, pregelatinized
starch S to 75%, starch, barium sulphate, magnesium trisilicate,
aluminium h:~rdroxide .
Inclusion o:E a filler having a negative heat of solution in
water, for example mannitol, sorbitol and xylitol, provides
tablets which, in addition to being water-dispersible, are
especially auitable for chewing in the mouth, the dissolving of
such an excipient in the saliva producing a cool, pleasant
sensation.
d) Lubricants: Generally lubricants are used in as low an amount as
.possible. Examples of lubricants with percentage weights which
are suitable for a tablet are: stearates (e.g. magnesium or
calcium ste,arate) 0.2 to 5% w/w, preferably 0.25 to 1% w/w, talc
0.19 to 5% w/w, preferably 1 to 2% w/w, polyethylene glycol 0.19
to 5% w/w, preferably 2 to S% w/w, liquid paraffin 0.18 to 5%
w/w, preferably 2 to 5% w/w, sodium lauryl sulphate 0.19 to 5%
w/w, preferably 0.5 to 2% w/w, magnesium lauryl sulphate 0.12 to
5% w/w, preferably 1 to 2% w/w, colloidal silicon dioxide 0.1 to
5% w/w, preferably 0.1 to 1.0% w/w, palmitostearate 0.01 to 5%


CA 02277722 2000-08-02
- 17 -
w/w, preferably 1 to 3% w/w, stearic acid 0.01 to 5% w/w,
preferably 1'to 3% wfw, zinc stearate 0.01 to 2% w/w, 0.5 to 1.5%
w/w, hydrogenated vegetable oil 0.5 to 5% w/w, preferably 1 to 3%
w/w. More suitably the lower value is 0.25%.
e) Wetting agents/surfactants: examples with suitable amounts are:
sodium dodecyl sulphate 0 to 10% w/w, preferably 0.5 to 2% w/w,
sodium lauryl sulphate 0 to 10% w/w, preferably 0.1 to 3.0% w/w,
polyoxyethylen.e sorbitan fatty acid esters (Tweens) 0 to 3% w/w,
preferably 0.05 to 1.~~% w/w, polyoxyethylene stearates 0 to 2%
w/w, preferably 0.05 to 1.0% w/w, sorbitan fatty acid esters
(Spans) 0 to 3% w/w, preferably 0.05 to 1.0% w/w.
f) Glidants: for example, talc 0 to 5% w/w, preferably 1 to 2% w/w,
starch 0 to 15% w/w, preferably 2 to 10% w/w, magnesium stearate
up to 5%, preferably 0 - 2.0% w/w, silica derivatives generally 0
to 1% w/w, preferably ~7.2 to 0.5% w/w, such as colloidal silica
(e. g. Aerosil) 0 to 0-5% w/w, preferably 0.25 to 3% w/w,
pyrogenic silica 0 to 2% w/w, preferably 0.25 to 1% w/w, hydrated
sodium silicoaluminate 0 to 2% w/w, preferably 0.5 to 1% w/w,
colloidal silicon dioxide 0 to 0.5% w/w.
g) Flavouring agents: are used in for example approximate quantities
of 0 to 5% wfw, preferably 0.25 to 2% w/w, orange, cherry and
strawberry, raspberry, grape and passion fruit.
h) Sweetening agents: far example sodium saccharin 0 to 10% w/w,
preferably, 0.5 to 5.0% w/w, aspartame 0 to 10% w/w, preferably
0.25 to 5.0% w/w, confectioners sugar 0 to 30% w/w, preferably 5
to 20% w/w, sorbitol 25 to 90% w/w, preferably 0.5 to 10% w/w,
sucrose 0 to 85% w/w, preferably 0.5 to 20% w/w, xylitol 0 - 20%
w/w, preferabl.y 0.5 to 10% w/w.
Tween, Aerosil and Span are Trade-marks:

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WO 92/13527 PCT/GB92/00163
- 18. -
Such materials may be incorporated at the appropriate stages) of the
manufacturing process together with any other agents (e. g.
colourants).
Based on the teachings and principles set out herein, the following
general formulations are illustrative of tablets of the invention, and
the skilled man given these teachings and principles will be able to
make specific tablet formulations in accordance with the invention.
INGREDIEN'.f CONCENTRATION (% w/w)
in Tablet
Active compound 5 to 90


Swellable clay 0.25 to 60 (preferably 0.25
to 50)


Binder 0 to 25


Disintegrating af;ent 0 to 20


Water-soluble filler 0 to 95


Water-insoluble :Filler 0 to 95


Wetting agent 0 to 5


Lubricant 0.1 to 5


Colours, flavours, sweeteners0 to 10


Approximate Tablet weight: 50-2000mg





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Other aspects of the tablet preparation will now be discussed.
Suitably the dry mixing is effected with a mixing time of 5 minutes to
25 minutes preferably about 10 minutes.
The swellable clay can be dry mixed with the active compound and other
excipients and then granulating solution added, or the clay and other
excipients can be dispersed firstly in the granulating solution and
then added to the active compound and any other excipients prior to
granulation.
The liquid employed to moisten the dry mixture, prior to the
granulation step, is preferably aqueous, for example water or a
mixture of water and a suitable alcohol such as ethanol or
isopropanol.
Wet mixing or granulating times which are suitable (depending on the
type of mixer used) are 5 to 20 minutes.
Suitable granule drying times and conditions (which will vary
according to the type of equipment used and batch size of granules)
are about 50 to 8'0°C, (using a dryer such as with a tray or fluid bed
dryer) to obtain a moisture content generally below about 4~.
Generally suitable compression weights and final table hardness will
vary according to the size of tablet, but generally suitable values
are as follows:

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- 20 -
Approximate Approximate Approximate


Tablet weight Tablet Target tablet


(mg) diameter hardness


(KP)


60 5.6 1-2


80 6.4 3-4


125 . 7.4 4-5 _


250 8.6 S-6


330 9.4 6-g


500 11.0 10-12


600 11.8 10-14.


1000 14.0 12-16


The tablets may optionally be film-coated, for example with
hydroxypropylmethyl cellulose, polyethylene glycol or titanium
dioxide, and/or may be scored and/or may be polished, for example with
polyethylene glycol 8000. If the tablets are film-coated, this .makes
them easier to swallow or chew (i.e. the tablets are suitable for
either dispersion in water or for direct swallowing or chewing), but
the dispersion time is increased.
The present invention also provides:


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. - 21 -
a) Granules containing an active compound and a pharmaceutically
acceptable swellable clay, suitable for use in the preparation of
a Water-dispersible tablet according to the invention.
b) Use of granules as defined above in the preparation of a
water-disper~~ible tablet according to the invention. Optionally,
a further amount of swellable clay may be added after granulation
and before compression;
c) Use of a pharmaceutically acceptable swellable clay as a
dispersing agent in the preparation of a water-dispersible tablet
containing an active compound (as defined above);
d) Use in human medicinal therapy of a water-dispersible tablet
comprising an active compound (as defined above), together with
an effective amount of pharmaceutically acceptable swellable clay
within the granules of the tablet.
Suitably the swell.able clay of the invention is a pharmaceutically
acceptable crystalline minezal compound, such as aluminium magnesium
silicate (e.g. Vee:gum).
The therapeutic c4se of a tablet of the invention includes both
treatment and prophylaxis.
The invention ha~~ been found to have particular application with
lamotrigine becaur~e of t:he long term instability of lamotrigine in
aqueous media. Furthermare dispersible tablets containing lamotrigine
have been found t:o give a finer dispersion than tablets using more
common disintegrating agents such as Explotab.
Further aspects of the invention illustrated with respect of
lamotrigine are:


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e) Granules, suitable for use in the preparation of a
water-dispersible compressed tablet, comprising lamotrigine or a
pharmaceuti<:ally acceptable salt thereof together with a
pharmaceutically acceptable crystalline mineral clay as
dispersing agent;
f) Use of granules as defined above in the preparation of a
water-dispersible compressed tablet which may involve the
addition of a further amount of crystalline mineral clay compound
after granu:Lation and before compression; and
g) Use of a pharmaceutically acceptable crystalline mineral clay as
dispersing agent in the preparation of a water-dispersible
compressed tablet containing lamotrigine or a pharmaceutically
acceptable ::alt thereof.
h) A water-dispersible tablet comprising lamotrigine or a
pharmaceutically acceptable salt thereof together with a
pharmaceutically acceptable crystalline mineral clay having a
lattice stricture which expands upon hydration as dispersing
agent. The lamotrigine or a pharmaceutically acceptable salt
thereof togeaher with the mineral' clay are comprised within the
tablet in granulated form. .
i) A method for the preparation of a lamotrigine water-dispersible
tablet which comprises the steps of
admixture :in dry, finely-divided form of lamotrigine or a
. pharmaceutically acceptable salt thereof and the pharmaceutically
acceptable crystalline mineral clay which may be chosen from the group
consisting of attapulg:ite, smectite and mont~orillonoid clays or
magnesium aluminium silicate,
optional addition of other pharmaceutical ingredients such as
fillers (~ lactose, av:icel or mannitol), disintegrants, binders, etc.


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addition of a quantity of a pharmaceutically acceptable liquid
sufficient to moisten the mixture,
granulation of the resulting moist mass,
drying of the granules and blending of the granules with optional
lubricants, glid;ant, flavours, disintegrants etc., and
formation o:f the blend into a tablet.
j) Use in human medicine of a water-dispersible compressed tablet
comprising Lamotrigine or a pharmaceutically acceptable salt _
thereof together with a pharmaceutically acceptable crystalline
mineral clay as dispersing agent, and
k) A method four the treatment in a human being of a disorder of the
central nervous system which comprises administration of a
water-dispersible compressed tablet comprising lamotrigine or a
pharmaceuti~~ally acceptable salt thereof together with a
pharmaceuti~~ally acceptable crystalline mineral clay as
dispersing .agent.
Especially preferred tablets are those wherein the lamotrigine is
present as the base.
The said tablets may be employed in human medicine in the treatment of
disozders of the central nervous system and in particular in the
treatment of epileptic seizures. They may be administered one or more
times per day, for example up to five times per day, at the discretion
of the attendant physician and dependent upon the age and condition of
the patient, the particular disorder being treated, the unit dose
adopted and the total dose required. A suitable daily dose for the
treatment of epileptic seizures will generally lie in the range of 5
to 500 mg., more often in the range of 25 to 400 mg., calculated as
the base.


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 24 -
The physical size of the said tablets is desirably such as to permit
their dispersion, prior to oral ingestion, in an acceptably small
volume of water. Thus, for example, a tablet containing 5 mg.
(calculated as the base) of lamotrigine or a salt thereof, a dose
especially suitable for paediatric use, is advantageously small enough
to disperse in tine volume of water .held in a standard 5 ml. medicine
spoon.
Tablets of the invention containing lamotrigine (or a salt thereof)
advantageously include a magnesium aluminium silicate such as Veegum F
as the swellable clay together with further optional pharmaceutical _
carriers or excipients referred to above such as binders, lubricants,
fillers, disintegrating agents etc.
In such tablets the ingredients are advantagously present in the
following proportions: lamotrigine: 2% w/w to 90% w/w preferably 5%
w/w to 40% w/w; swellable clay: 0.25% w/w to 40% w/w preferably 0.25%
W/W t0 lO$ w/w.
A suitable formulation of a dispersible tablet containing 25 to 200mg
lamotrigine wou7Ld be

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 25 -
Lamotrigine 30% w/w to 50% w/w, preferably 35-45%
Calcium carbonate 26% w/w to 4b% w/w, preferably 31-41%
LHPC-LH11 5% w/w to 30% w/w, preferably 5-15%
or microcrys-
talline
cellulose (e. g.
Avicel PH101)
Magnesium 0.2-'i% w/w to 30% w/w, preferably 0.25-10%
aluminium
silicate
Veegum F or
bentonite
Povidone 0.25% w/w to 5.0% w/w, preferably 0.5-2%
or pre-
gelled starch 1.0% w/w to 8.0% w/w, preferably 2-5%
Sodium starch
glycollate 0% w/w to 8% w/w, preferably 0-5%
Magnesium 0.25% w/w to 2% w/w, preferably 0.25-1%
stearate
and if optionally film coated:
Opadry 0.1%-w/w to 2% w/w, preferably 0.25-1%
Polyethylene 0.1% w/w to 0.5% w/w, preferably 0.1-0.2%
glycol 8000

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 26 -
A suitable formulation of a dispersible tablet containing Smg to 50mg
of lamotrigine would be as follows, (values being in $ w/w).
Lamotrigine 3-13 preferably S-11
Lactose or 50-60 preferably 53-59
calcium carbonate
Microcrystalline 20-35 preferably 24-30
cellulose (e. g.
Avicel PH101)
or LHPC-LH11
Sodium starch 0-8 preferably 0-5
glycollate
Magnesium aluminium 0.25-30 preferably 0.25-10
silicate
Veegum F or
bentonite
Povidone K30 0.25-5.0 preferably 0.5-2.0
or pregelled
starch 1..0-8.0 preferably 2-5
Sodium docusate 0-0.5 preferably 0.5-0.15


Sodium saccharine 0-3 preferably 0.5-2.


Magnesium stearate0.25-2 preferably 0.25-1
---


and if optionally coated _
f.'ilm


Opadry C1.1-2.0 preferably 0.25-1


Polyethylene glycolØ1-0.5 preferably 0.1-0.2


8000




CA 02277722 1999-08-OS
WO 92/1352 i PCT/GB92/00163
- 27 -
As referred to above, the present invention is particularly applicable
to the formulation of water-dispersible tablets containing acyclovir
as the active .compound.
Acyclovir is a compound which has been found to have potent activity
against viruses of th.e herpes family, particularly herpes simplex and
herpes varicella roster. Such activity has been demonstrated by the
outstanding success of acyclovir in the therapeutic treatment of
clinical conditions such as genital herpes caused by the herpes
varicella roster virus.
In the treatment of certain conditions, it may be necessary to
administer acyclovir to the patient in relatively large dosages to
achieve the effective therapeutic levels of drug in the plasma,
particularly when oral administration is desired. For example, in the
treatment of shingles, it is recommended to administer acyclovir at a
dosage regime of 800mg five times per day. A tablet formulation
containing 800mg of acyclovir is currently available but its
relatively large size sometimes renders it difficult to swallow by
elderly patients, such patients being particularly susceptible to
shingles. This problem is obviated by the water-dispersible tablets
according to the invention which enable relatively high doses of
acyclovir to be administered in a drinkable dispersion by the oral
route.
The,advantageous water-dispersibility' of tablets according to the
invention containing acyclovir as the active compound is especially
surprising in view of the poor water-dispersibility demonstrated by
tablets containing canventional disintegrating agents such as sodium
starch glycollate, cross-linked povidone and cross-linked sodium
carboxymethylcellulose.
Yet further aspects of the invention with respect to acyclovir are as
follows:


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
_ 28 _
1) A granulate comprising acyclovir together with a pharmaceutically
acceptablE: magnesium aluminium silicate compound;
m) Use of a granulate according to e) above for the manufacture of a
water-dispersible tablet formulation.
n) Use of magnesium aluminium silicate in the manufacture of a
water-dispersible tablet formulation of acyclovir.
o) A water-d:Lspersible pharmaceutical.tablet formulation comprising
acyclovir together with a pharmaceutically acceptable magnesium
aluminium silicate compound.
p) A process for the preparation of a pharmaceutical tablet
formulation which comprises admixing acyclovir with a magnesium
aluminium silicate compound and optionally one or more further
pharmaceur_ical carriers or excipients, granulating the resulting
mixture with a pharmaceutically acceptable liquid, drying the
resulting granulate, optionally mixing the dried granulate with
one or more further pharmaceutical carriers or excipients, and
subsequenvtly compressing the dried granulate to form tablets.
The liquid employed in the above granulation step is
advantage~~usly aqueous, for example, an aqueous ethanol mixture.
The resulting tablets may be subsequently film coated for example
with hydroxypropylmethyl cellulose, titanium dioxide or
polyethylene glycol and, if desired, polished for example with
polyethylene glycol 8000. ,
Tablets according to the invention containing acyclovir advantageously
include a magnesium aluminium silicate such as Veegum F as the
swellable clay optionally together with further pharmaceutical
carriers or excipients referred to above such as disintegrating
agents, binders, fillers, lubricants etc.


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 29 -
In such tablets the ingredients are advantageously present in the
following proportions: acyclovir 40 to 98% w/w, preferably 75 to 85%
w/w, swellable clay 0.'_i to 40% w/w, preferably 0.5 to 10% w/w.
A suitable formulation of an acyclovir dispersible tablet containing
from 200mg-800mg; acyclovir would be:
Acyclovir 70% w/w to 90% w/w, preferably 75-85% w/w
Povidone 0.25% w/w to 5% w/w, preferably 0.5-2% w/w
or pregelled
starch
Magnesium 0.5% w/w to 30% w/w, preferably 0.5-10% w/w
aluminium
silicate
Veegum F or
bentonite
Microcrystalline: 5% w/w to 25% w/w, preferably 5-15% w/w
cellulose
Avicel PH101
or LHPC-LH1I
Sodium starch 0% w/w to 8% w/w, preferably 0-5% w/w
glycollate
Magnesium 0..?5% w/w to 2% w/w, preferably 0.25-1.0% w/w
stearate
and if optionally film coated:
Opadry O.:L% w/w to 2% w/w, preferably 0.25-1.0% w/w
Polyethylene 0.1% w/w to 0.5% w/w, preferably 0.1-0.2% w/w
glycol 8000


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 30 -
The following Examples illustrate the present invention.
Examples 1 to 6 and 2:9 are comparative examples while examples 7-28,
30 and 31 describe the preparation of tablets according to the
invention in which the active comvound is acvclovir.
Example 1. 2 3 4


Number m ~tablet g/tabletmg/tabletme/tablet
m


Intra-granular,:


Acyclovir * 848.0 848.0 844.0 844.0


Avicel PH101 60.0 NIL 101 NIL


Lactose 1.20.0 NIL NIL NIL


Starch (maize) NIL NIL 50 NIL


Explotab NIL 75.0 50 NIL


Primogel NIL NIL NIL 75.0


Ac-Di-Sol 83.0 NIL 23 NIL


Kollidon CL starchNIL NIL NIL NIL


Saccharin sodium20.0 10.0 NIL NIL


Sodium lauryl 5.0 NIL 3.0 NIL


sulphate


Sodium docusate NIL 1.0 NIL 0.5


Dicalc.phosph.dihyr. NIL NIL 200.0
NIL


Povidone K30 NIL 10.0 22 11.2


Extra-granular:


Ac-Di-Sol 40.0 NIL NIL NIL


Avicel PH102 60.0 94 NIL NIL


Amberlite 1RP88 NIL NIL NIL 50.0


Kollidon CL NIL NIL 60.I NIL


Mg'stearate _ 12.0 I0.0 10.1 11.0


Tablet weight 11:48.0 1048.0 163.2 1191.7
(mg) 1


* In the follo wing examples exceptexamplesI3, 14 and 15, the


actual qv.anti ty of ovir is calculated so
acycl used from
a factor


as to prawide 800mg acyclovirper tablet. for
of (The
factor


acyclovi=' is typically105.5 100 acyclovir).In
equivalent
to


examples I3, 14 and the actualquantityof acyclovir was
15, used


adjusted from the factorso as provide per
to 800mg
of acyclovir


tablet.



CA 02277722 1999-08-OS
WO 92/13527 PC1"/GB92/00163
- 31 -
Example 5 6 7 8 9


Number mg/tablet mg/tabletmg/tabletmg/tablet mg/tablet



Acyclovir 844 .0 848.0 844.0 848.0 848.0


Avicel PH 101 101.0 83.46 100.0 89.0 89.0


Veegum F NIL NIL 53.0 53.0 53.0


Sodium starch 90.0 39.37 42.0 42.0 42.0


glycollate


(Explotab)


Povidone K30 11.0 10.27 NIL 11.0 11.0


Magnesium 9..'~ 8.85 9.4 9.4 9.4 _-


stearate


Film coat composite 1:


Opadry NIL NIL NIL NIL 7,86


Film coat composite 2:


Polyethylene glycol


8000 NIL NIL NIL NIL 2.097


Tablet weight 1055.5 989.95 1048.4 1052.4 1062.4


(mg)


In accordance With the invention, that the
to illustrate


disintegration time remains substantially
constant
at different
tablet


hardnesses, th,e formulation of Example was compressed
7 at


app=oximately 8 kp (7a), 12 kp (7b) and 18 (7c) and
kp the results


noted hereafte=.



CA 02277722 1999-08-OS
WO 92/I3527 PCT/GB92/00163
- 32 -
Examp 1 1.0 11 12
a


Number mg/tablet mg/tablet mg/tablet


Acyclovir 848.0 848.0 848.00


Avicel PH 101 118.5 71.1 86.8


Veegum F 26.5 * 53.0 53.0


Primojel 42.0 42.0 42.0


Povidone K30 NIL 20.9 5.2


Magnesium , 9.4 9.4 9.4


stearate



Tablet weight 1044.4 1044.4 1044.4


(mg)


* Veegiam added as a paste - example contains no PVP-K30 as a
binder. ~ '

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 33 -
Examyles of Acyclovir formulations
Example 13 14 15
Number mg/tablet mg/tablet mg/tablet
Component
(mg/tablet)
Acyclovir 800.0 800.0 800.0
Avicel PH 101 100.0 89.0 89.0
Veegum F 53.0 53.0 110.0


Sodium starch 42.0 42.0 42.0


glycollate


Povidone K30 NII. 11.0 11.0


Magnesium 9.4 9.4 9.9


stearate



Tablet weight


(mg) 1004.4 1004.4 1061.9



CA 02277722 1999-08-OS
WO 92/13527 PCT/G892/00163
- 34 -
Example 16 17 18 19


Number $ w/~a mg/ 8 w/w mg/ $ w/w mg/ ~ w/w mg/


tablet tablet tablet tablet


Acyclovir 79.95 848.0 75.54 795.00 65.47 689.00 55.00 583.00
Avicel
PH101 8.8~5 89.0 8.86 89.00 8.86 89.00 8.86 89.00
Veegum F 5.28 53.0 10.00 106.00 20.00 212.00 30.00 318.00
Explotab 4.1~~ 42.0 4.18 42.00 4.18 42.00 4.18 42.00
Povidone 1.09 11.0 1.09 11.00 1.09 11.00 1.09 11.00
K30
Magnesium 0.'94 9.4 0.94 9.40 0.94 9.40 0.94 9.40
stearate
Tablet
weight 100:3 1052.4 100.0 1052.4 100.0 1052.4 100.0 1052.4
~mg)

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/04163
- 35 -
Example 20 21 22
Number % w/w mg/ % w/w mg/ % w/w mg/
tablet tablet tablet
Acyclovir 45.32 477.00 84.3 890.00 44.93 848.00


Avicel PH1018.86 89.00 8.86 89.00 8.86 157.76


Veegum F 40.00 424.00 1.00 10.60 40.00 712.22


Explotab 4.18 42.00 4.18 42.00 4.18 74.43


Povidone 1.09 11.00 1.09 11.00 1.09 19.41
K30


Magnesium 0.94 9.40 0.94 9.40 0.94 16.74
stearate
Tablet weight
(mg) 100.00 1052.4 100.00 1052.4 100.00 1828.56

CA 02277722 1999-08-OS
WO 92/13527 PC1"/GB92/00163
- 36 -



Example 23 24 25
26


Number % w,/w mg/ % w/w mg/ % w/w mg/ % w/w mg/


tablet tablet tablet tablet


Acyclovir 65.47 689.00 55.00 583.00 45.32 477,00 79,65 848.00
Avicel 8.fl6 89.00 8.86 89.00 8.86 89.00 8.86 89.0
PH101
Veegum F *20.C10 (106.00 *30.00 (159.00 *40.00 (212.00 5.28 53.0
(106..00 (159.00
(212.00
Explotab 4,1.8 42.00 4.18 42.00 4.18 42.00 4.18 42.0
Povidone 1.09 11.00 1.09 11.00 1.09 11.00 1.09 11.0
K30
Magnesium 0.94 9.40 0.94 9.40 0.94 9.40 0.94 9.4
stearate
Tablet
weight 100.00 1052.4 100.00 1052.4 100.00 1052.4 100.00 1052.4
(mg)
* In these examples the Veegum is distributed equally both
intra-granularly and extra-granularly.

CA 02277722 1999-08-OS
WO 92/13527 PCZ'/GB92/00163
- 37 -
Example 27 28 29 30 31


Number % w/w mg/ % w/w mg/ % w/w mg/ mg/ mg/


tablet tablet tablet tablettablet


Acyclovir 84.43 848.00 84.68 848.00 84.93 848.00 848.0 840.0
Avicel 8.86 83.95 8.86 83.70 8.86 83.46 89.0 89.0
PH101
Veegum F 0.50 4.74 0.25 2.36 0.00 0.00 - -


Bentonite - - - - - - 53.0 NIL


Attapulgite - - - - - - NIL 53.0


Explotab 4.18 39.60 4.18 39.49 4.18 39.37 42.0 42.0


Povidone 1.09 10.32 1.09 10.30 1.09 10.27 11.0 ~ 11.0


K30


Magnesium 0.94 8.91 0.94 8.88 0.94 8.85 9.1 9.1
stearate
Tablet
weight 100.00 995.53 100.00 992.73 100.00 989.95 1052.1 1044.1
(mg)

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 38 -
Examples 32-40 describe the preparation of tablets according to the
invention in which the active compound is lamotrigine.
Example 32 33 34 35 36 37 38


Number mg/ mg/ mg/ mg/ mg/ mg/ mg/


tablettablettablet tablet tablettablet tablet



Lamotrigine 100 5.0 5.0 100 100 100 100


Calcium


carbonate 95 NIL NIL NIL 95 NIL NIL


Lactose NIL 34 35.0 15 NIL 98.1 84


L HPC-LH11 25 NIL NIL NIL 25 NIL NIL
_


Veegum F 12 3.0 3.0 7.5 12.0 16.0 12


Povidone K30 3.0 0.6 0.6 1.5 3.0 3.2 3


Explotab 10.0 2.0 1.2 6.0 NIL 12.8 10.0


Sodium


Saccharin 2.5 0.5 0.5 NIL NIL NIL NIL


Aspartame NIL NIL NIL 4.0 7.5 NIL 7.5


Microcrys talline


cellulose


(Avicel PH101)NIL 17 17 15 NIL 89.6 23


Sodium docusateNIL 0.05 NIL NIL NIL 0.26 0.2


Magnesium


stearate 2.5 0.4 0.4 1.5 2.5 3.2 2.5



Tablet weight


" (mg) 250 62.55 62'.70 150.5 245 323.16 242.2



CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 39 -
Example
Number 39 40
Lamotrigine 100.0 100.0


Calcium


carbonate 95.0 90.0


Lactose


L HPC-LH11 25.0 25.0


Veegum F 12.0 12.0


Povidone K30 3.0 3.0


Explotab - 10.0


Sodium


Saccharin - -


Aspartame 7.5 7.5


Microcrys talline:


cellulose


(Avicel PH101)- -


Sodium docusate- -


Magnesium


stearate 2.5 2.5


Flavour - 1.24


Tablet weight
(mgs) 245.0 251.24

CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 40 -
Examples of Tablet Formulations
containing other Active Compounds
Examp 1 a
Number 41 42 43 44 45
Active compound


(mg) 200.0 300.0 758.0 500.0 5.0


Avicel PH101 50.0 64.0 83.0 - 17.0


Explotab 12.3 21.0 40.0 27.0 2.5


L-HPC-LH11 50.0 - 41.0 87.0 -


Lactose - 110.0 - - 34.0


Veegum F 16.7 27.0 50.0 71.0 3.0


Citric acid


monohydrats; - - 0 , 8 -


Na docusatc: - - Q,8 - -


Saccharin


sodium - - 0.5 - -


Povidone K:30 3.3 10.8 20.0 20.0 0.7


Magnesium 1.0 2.7 5.0 2.0 0.4


Stearate


Flavour (P:ineapple) - - 2.0 -


Tablet Weight 333.3 535.5 1001.1 707.0 62.6


(mg)


* The active compound for Example as follows:-
each is


Example 41 - 1-(~-D-arabinofuranosyl)-5-propynyluracil



Example 42 - Allopurinol


Example 43 - 2-(4-(4-chlorophenyl)cyclohexyl]-3-hydroxy-
1,4,nap-


thoquinone


Example 44 - Paracetamol


Example 45 - Diazepam




CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 41 -
Iiethod of Preoarat on
The tablets described in Examples 1-45 above Were prepared according
to the following general method:
(a) A dry mixture was made of all components except Povidone/PVP K30,
sodium do~:usate (if present) and magnesium stearate;
(b) The Povid~~ne/PVP K30 and sodium docusate (if present) were
dissolved in 50% aqueous alcohol to form a granulation solution;
(c) The granulation solution was added to the dry mixture to form
granules;
(d) The wet granules were dried in a fluid bed dryer;
(e) The granules were then sifted through a 1000~sm diameter mesh
sieve; and
(f) The dried granules were blended with the magnesium stearate and
compressed to form tablets.
Flavouring agents where present were added at blending step (f) above.
This general method is illustrated with respect to the following
specific examples.
example 8 : Uncoated ab ets
(a) A dry mixture was made of all components except Povi-done/PVP K30
and magnesium stearate using a Diosna P100 (high shear mixer -
granulator) for 3 minutes.
(b) The Povid.one/PVP K30 was dissolved in 50% aqueous alcohol to form
a granulation solution.


CA 02277722 1999-08-OS
WO 92/13527 PCT/G892/00163
- 42 -
(c) The granulation solution was added to an approximate quantity of
300m1 per k,g dry weight to the dry mixture to form granules. Wet
mixing was .carried out for approximately 5 minutes.
(d) The wet gravnules were dried in an Aeromatic T3 fluid bed drier at
a temperature of 70°C for approximately 3 0 minutes. The moisture
content of the granules was approximately 4%.
(e) The granules were then sifted through a 1000um diameter mesh
sieve using a Jackson Crockatt No.7 sifter.
(f) The dried granules were blended with the magnesium stearate using
a collette mixer for approximately 10 minutes and compressed to
form tablets using a Manesty D3 Rotary tablet press fitted with
caplet shaped punches of approximately 19.3mm length and 9.Omm
breadth. Tablets were compressed to a weight of 1052mg ~ 2%.
This granule can be used to make other strengths of acyclovir
dispersible tablets, e.g. 200mg and 400mg, compressing the dried
granules to a weight of respectively 263mg and 526mg, using round
punches with diameters of respectively ll.Omm and 8.6mm.
Examvle 9 : Film Coated Tablets
Steps (a) to (f) described in Example 8 were repeated to form an
uncoated tablet which was then film-coated by the following procedure.
The film-coating; apparatus used was a Manesty Accellacota 10. The
coating suspension was; sprayed onto the tablet cores to a target
weight increase of between 0.5 - 1.0% using suitable parameters of:
pan rotation speed (8.5 rpm)
spray (appl.ication rate (-20g per min)
inlet temperature (-75°C)
exhaust temperature (-53°C).


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 43 -
A polish coat of PEG8000 was then applied to the film-coated tablets,
to a further. weight gain of 0.1 - 0.2%.
Examvles 13 to 15
In Example 13, Acyclovir, Avicel PH101, Sodium starch glycollate and
Veegum F are dry mixed in a mixer. The mixture is then granulated
after adding a sufficient volume of 50% aqueous alcohol (IMS). The
resulting granules are: dried, blended With the magnesium stearate and
then compressec! to form tablets.
Example 14
The procedure described in Example 13 for the preparation of the
granules and formation of the tablets is employed except that
granulation of the dry mixture is effected with the Povidone in a 50%
aqueous alcohol. solution. Film coating of the resulting tablets can
be optionally effected by treating the tablets with a dispersion of
Opadry white dispersion in purified water and drying the coated
tablets which are subsequently polished with a solution of
polyethylene glycol 8000, USNF in 50% aqueous alcohol (IMS).
For Example 1_°°~, the procedure described in Example 13
for the
preparation of the granules and formation of the. tablets is employed
except that granulation of the dry mixture was effected with the
Povidone in a .'~0% aqueous alcohol solution.
Examvle 33
(a) A dry mixture was made of all components except Povidone/PVP K30
and magnesium stearate using a Z-blade Morton Mixer, mixing for
minute~~ at a slow speed.
(b) The Povidone/PVP K30 was dissolved in 50% aqueous alcohol to form
a granulation solution;


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 44 -
(c) The granulation solution was added to an approximate quantity of
350m1 per kg dry weight to the dry mixture to form granules;
(d) Wet mixing was carried out for approximately 10 minutes. The wet
granules were sieved through a 2000~m mesh sieve;
(e) The wet granules were dried in an Aeromatic fluid bed drier at a
temperature of 70°C for approximately 25 minutes;
(f) The granules were then sifted through a 1000~cm diameter mesh
sieve;
(g) The dried. granules were blended with the magnesium stearate using
a Rotomix.er rotary blender for 5 minutes and compressed to form
tablets Using a~ Manesty D3 Rotary press fitted with 5.6mm
diameter round (normal curvature) punches and dies. Tablets were
compressed to a weight of 62.55mg ~ 2%.
Flavouring agents may be added at blending step (g) above. .
For a 50mg tat~let,.the same procedure was used, except that a die of
ll.Smm diameter was used and the tablets were compressed to a weight
of 625 . 5mg ~ 2 % .
The lamotrigine tablets could be optionally film coated using the same
procedure as described for Example 9.
The tablets prepared in accordance with the above Examples were then
tested as follows.
Tablet Evaluation Methods
1. Avera~,e~~ tablet weig h. Twenty tablets were weighed on an
analytical balance and the average tablet weight calculated.


CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 45 -
2. Tablet breaking, strength (kilo pond-ktl, 5 tablets were
individually tested using a Schleuniger crushing strength tester,
and the average breaking strength calculated.
3. Friabilitv (~s loss). 10 tablets, accurately weighed, were
subjected to 10 minutes friability testing using a Roche
Friabilato:r. The tablets were dedusted, reweighed, and the
weight loss due to the friability was calculated as a percentage
of the initial weight.
4. Dispersion Disintegration time DT (BP 1988). 6 tablets were
tested in .accordance to the above-defined BP test (without discs)
for dispersible tablets. This utilises water at a temperature of
19-2I°C.
5. Dispersion ualit~v. In accordance with the BP uniformity of
dispersion test for dispersible tablets (BP 1988 Volume II page
895), two tablets were placed in 100m1 of water at 19-21°C and
allowed to disperse. A smooth dispersion was produced which
passed through a '710~m mesh sieve.
~anule Evaluation Methods
1. Loss on D~.-ving (LOD). The residual moisture content of the
granule (LOD) was determined on a 3-4g sample using a Computrac
moisture analyser set to 90°C operated in accordance with the
~- manufacturer's procedure.
2. Weight Median Diameter (WMD). A lOg sample of granule was sifted
for 2 minutes at suitable pulse and sift amplitudes in an Allen
Bradley sonic sifter in accordance with manufacturer's
instructio~zs. Sieves of 710~m, SOOUm, 355~cm, 250~cm, 150~m, 106~m
and 53~cm were used. The WMD was calculated from the cumulative
percentage undersize size distribution using a computer
programme.

CA 02277722 1999-08-OS
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CA 02277722 1999-08-OS
WO 92/13527 PCT/GB92/00163
- 52 -
A particle size analysis was carried out on the dispersion of a tablet
of Example 9 in ac:cordance with the following method.
The particle size distribution was determined using a Malvern 2600
particle analyser as follows. The instrument was set to analyse
particles in liquid with magnetic stirrer fitted. A 300mm focal
length lens was used.
1. Disperse tablet in 'LOOml of de-ionised water.
2. Agitate solution for approximately 2 hours.
3. Filter or centrifuge solution to obtain liquor which should be
saturated with all ingredients present in the tablet.
4. Disperse second tab'Let in 50m1 of saturated liquor allowing 3
minutes to i=ully disperse. Agitate vigorously and remove a
sample of the dispersion within 5 minutes adding sufficient
Quantity to ~=he Malvern PIL cell containing the liquor to obtain
an observation valu~a of 0.15-0.30. Analyse sample.
The particle size distribution was as follows:
Particle size: (as equivalent spherical volume)
<710~m - 100%
<300~m - 98.7%
<200~cm - 86.7% -
<130~m - 50% (med:Lan particle size).

Representative Drawing