Note: Descriptions are shown in the official language in which they were submitted.
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Merck Patent Gesellschaft
mit beschrankter Haftung
6100 D a r m s t a d t
Desiccant tablet
The invention relates to a coated desiccant
tablet (DT), this coating containing as the essential
cons~ituen~ a water-soluble film-former.
It is known to employ DTs when pac~aging pharma-
ceuticals which are sensitive to moisture. For example,
tablets which are sensitive to moisture can be incor-
porated into packaging Lmpe~meable to w~ter vapor, the
packaging containing, besides the pharmaceutical tablets,
an additional desiccant unit in the foDm of a tablet.
Known DTs have the di~advantage that they create
pulverulent grindings, for example aused by vibrations
during transport, which can contaminate the pharma-
ceutical. Moreover, the DTs may be mistaken for the
pharmaceutical tablets.
~P-61/291,021 describes DT~ which are covered
with a thin layer of liquid resin or rubber, for example
also silicon~ rubber, where the pul~erulent grindings are
reduced. These tablets, in turn, have other disadvan-
tages, for example during their manufacture, which must
be carried out in a non aqueou~ medi~m.
The invention is based on the ob~ect to provide
a DT which does no~, or to a lesser extent~ have the
disadvantages of the known DTs. It was an essential part
of the object to find a coating process in which no
organic solvent is employed.
It has b~en found that ~he D~s can be pro~ided
with a coating which as an essential constituent contains
a water-soluble film formar. This coating preven~s
abrasion during handling, while drying speed and drying
capacity are nok substantially reduced.
The invention relates ~o a coated ~T, charac-
terized in that the coating contains as the esse~ial
constituenk a water-soluble film former.
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Suitable desiccants are in particular those which
do not change their volume upon uptake of water (which do
not swell), above all silica gelst mainly fine-pored
silica gels of a particle size in the range of between
about 200 and 400 ~m. Molecular sieves, aluminas or dry
clays are also suitable.
The desiccant can be compressed in a customary
manner to give tablets of about 50-5000 mg, preferably
100-500 mg. The tablet cores can contain conventional
binders, for example polyvinylpyrrolidone (PVP), and
o~her conventional additives. If PVP is used, a content
of 3-10~ by weight is preferred (based on the total
weight of ~he tablet cores). Higher amounts of PVP give
harder tablets, lower amounts of PVP give softer tablets.
Cellulose derivatives are preferred among the
water-~oluble film formers. A particularly highly sui-
table derivative is methylhydro~ypropylcellulose, fur-
thexmore, for example, methylcellulose, hydroxypropyl-
cellulose or sodium carbo~ymethylcellulose. It is also
po~sible for the coatings to contain a plurality of
various water-soluble cellulo~e derivatives. Other
suitable film formers are polyvinyl alcohol and PVP.
The coating of the DT can, according to the
invention, additionally contain one or more plasticizers.
Amongst these plasticizers, the water-soluble ones axe
likewise preferred, in particular polyalkylene glycols,
preferably pol~eth~lene glyools, such as polyethylene
glycol 400 or polyethylene glycol 6000. The following may
furthermore be mentioned: alkylene glycols, such as
propylene glycol ~1,2-propanediol~, esters~ fox example
trialkyl citrates, such as triet~yl citrate, or poly-
oxyethylene/pulyoxypropylene block polymer~.
The coating of the DT can, according to the
invention, additionally contain one or more pigments.
With the aid of these pigments, it is possible to impart
a colour to the DTs, preferably in such a w y that, if
appropriate, a clear distinction can be made between them
and the pharmaceutical tablets in the same ~ackaging.
Suitable pigments are all those which are conventional in
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pharmacy, for example oxides, such as titanium dioxide or
iron oxide; carbonates, such as calcium carbonate; or
coloured lacquers, such as Quinoline Yellow lacquer
E 104, Amaranth lacquer E 123 or Indigotin lacquer E 132.
These pigments have virtually no influence on the
permeability of the coating to water vapor.
The coating can contain further additives, for
example lubricants, such as talc or silicone oil, the
latter also in the form of an emulsion.
The coating is preferably applied in a thickness
of about 0.7 to 2.5 mg/cm2. Its proportion relative to
the total weight of the DT is about 1-5~ by weight.
Preferably, the DTs here have total weights between about
100 and 1000 mg.
The coating is applied according to the invention
in a conventional manner. Preferably, aqueous solutions
or suspensions which contain the desired constituents and
which are sprayed onto the tablet cores, preferably at
temperatures between 20 and 100, in particular between
50 and 80~ are used. Since the DT is capable of absorbing
water, the film coating can be applied in a~out 1/3 of
the conv~ntionally required tLme. Once the DT is coated,
the water contained therein can be removed through the
film coating without essential problems.
Drying is expediently carried ou~ at temperatures
bet~een 20 and 120, in particular between 50 and 80,
under reduced pr~ssure.
Example
2.0 kg of methylhydroxypropylc~llulose and
0.467 kg of polyethylene glycol 400 are dissolved in
22.0 kg of water. To this solution is added a suspension
of 0.333 kg of titanium~IV) oxide and 0.733 kg of Iron
Oxide Red in 7.8 kg of water, and the b tch is mixed and
sieved (sieve 180, Ph.Eur.).
The resulting suspension is sprayed, while
stirring, onto 90 kg of tablet cores preheated to 70,
each individual tablet core cons.t~ing of 190 mg of
silica gel, type E 0-400~ and 10 mg of PVP.
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The resulting coated DTs axe dried for 24 hour3
at 70-80 under reduced pressure.
No abrasion can be detected (Friabilator, type
"Roche", 10 minutes).
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