Note: Descriptions are shown in the official language in which they were submitted.
CA 02471102 2004-09-23
CRYSTAL FORM II OF CLARITHROMYCIN
Technical Field
'fh~is invention relates to a compound having therapeutic utility. More
particularly, the
present invention concerns 6-O-methyleryklltomycin A, Form I or Fozztt II
containing one or more
impurities, pharmaceutical compositions containing same and uses of samc as a
therapeutic
agent.
Bound of the Invention
6-O-methylerythromycin A (Clarithromycin) is a semisyttthetic macrolide
antibiotic of formula
W
....o
Ho- ~ o
0
CH
p
6-O-methyl erythromycin A
2o which exhibits excellent antibacterial activity against gram-positive
bacteria, some gram-
ztegative bacteria, anaerobic bacteria, Mycoplasma, and Chlamidia. It is
stable under acidic
conditions and is efficacious when administered orally. Clarithromycin xs a
useful therapy for
iztfections of the upper respiratory tract in children and adults.
Brief Description of the Drawines
2s FIGS. 1a, 1b and lc show, respectively, the powder ~ ray diffraction
spectrum, the
infrared spectrum, and the differtntial scanning calorimetric (DSC) thermogram
of 6-O-
methylerythromycin A Form I.
CA 02471102 2004-09-23
-2-
FIGS. 2a, 2b and 2c shorn, respectively, the powder X ray diffraction
spectrum, the
infrared spectrum and the differential scanning calorimetric (DSC) thermogram
of 6-O-
methylerythromycin A Form II.
Summary of the Invention
We have discovered that 6-O-methylerythromycin A can exist in at least two
distinct
crystalline forms, which for the sake of identification are designated "Form
I" and "Form II".
The crystal fortes are identified by their infrared spectrum, differential
scanning calorimetric
thermogram and powder x ray diffraction pattern. Form I and Form II crystals
have an identical
spectrum of antibacterial activity, but Form I cxystals unexpectedly have an
intrinsic rate of
1 o dissolution about three times that of Form II crystals. Investigations in
our laboratory have
revealed that 6-O-methylerythromycin A when recrystallized from ethanol,
tetrahydrofuran,
isopropyl acetate, at~d isopropanol, or mixtures of ethanol, te~ahydrofuran,
isopropyl acetate, or
isopropanol with other common organic solvents results in exclusive formation
of Form I
crystals, not identified hitherto.
15 Drugs currently on the market are formulated from the thermodynamically
more stable
Form II crystals. Therefore, preparation of the current commercial entity
requires converting the
Form I crystals to Form II. Typically this is done by heating the Form I
crystals under vacuum at
temperature of 8reater than 80°C, Therefore, the discovery of a novel
forth of G-O-
methylerythromycin A which can be prepared without the high temperature
treatment results in.
2o substantial processing cost savings. In addition, the favorable dissolution
charactezi.stics of
Form I relative to Form II increases bioavailability of the antibiotic and
provides significant
formulation advantages.
The present invention in one embodiment provides 6-O-methylezythromycin A Form
r or
Form II containing one or more impurities. In a preferred ezxibodiment, the
impurities are
25 selected from alkylated 6-O-methylerythromycin A compounds. In a more
preferred
embodiment of the invention, the aforementioned alkylated 6-O-
methylerythroznycin A
compounds are each alkylated at one or more of the 11, 12, 2', 3' and 4"
positions,
CA 02471102 2004-09-23
In a most preferred embodiment of the invention, the 6-O-methylerythrvmycin A
Form I
or Form IZ contains one or more of 6,11-di-D-methylerythromycin A, 6,12-di-O-
methylerythromycin A, and 6,4"-di-D-methylerythromycin A.
Also provided in accordance with the present invention are antibiotic
pharmaceutical
compositions comprising the products of the present invention together with a
phatxxtaceutically
acceptable carrier, as well as the use of such products as antibiotics yr in
the manufacture of
antibiotic medicaments.
Detailed Descriation
6-O-methylezythromycin A, is prepared by metbylation of the 6-hydroxy gtotxp
of
1o erythromycin A. However, in addition to the 6 position, erythromycin A
contains hydroxy
groups at the 11, 12, 2' and 4" positions, and a ztitrogen at 3' position, all
of ~cx~hich are potentially
reactive with alkyIating agents. Wherefore, it is necessary to protect the
various reactive
~unctionalities prior to alkylation of the 6-hydroxy group. Representative 6-O-
methylerythromycin A preparations are described in U.S. Pat. Nos. 4,331,803,
4,670,549,
is 4,672,109 and 4,990,602 and European Patent Specification 260 938 B 1.
Following Final removal of the protecting groups, the 6-O-methylerythromycin A
may
exist as a solid, a Semisolid, or a sytvp containing residual solvents from
the deprotection
reactions, inorganic salts, and other impurities. 6-O methylerythromycin A
Form I may be
crystallized directly from the syrup or semisolid using the solvents described
above.
20 Alternatively, if the crude reaction product solidiFes, the solid may be
recrystallized $om any of
the solvents described above. Pure 6-O-methylerythromyein A Form I may also be
obtained by
recrystallizing Form II or mixtures of Form I and Form II from any of the
solvent systems
described above. The term "6-O-methylerythromycin A" as used herein is meant
to include 6-O-
methylerythromycin A Form I ox II in any state of purity, or mixtures thereof.
25 The term "treating" refers to crystallizing or recrystallizing 6-O-
methylerykhromycin A as
defined above from any of the sol~rents described above.
CA 02471102 2004-09-23
-4-
The term "hydrocarbon" as used herein refers to straight chain or branched
alkanes
having the formula CnTTa"+Z. hydrocarbons useful in the solvent mixtures of
th,e present invention
include hexane, heptane, octane and the like.
The term "alkyl" refers to a monovalent group derived from a straight ox
branched chain
saturated hydrocarbon by the removal of a single hydrogen atom. Alkyl groups
axe exemplified
by methyl, ethyl, n- and iso-propyl, n-, sec-, iso- and tent-butyl, and the
like.
The term "ketone" refers to a solvent of formula RC(O)R' where R and R' are
straight or
branched alkyl. Ketones useful in the solvent mixtures of the present
invention include acetone,
methyl ethyl ketone, 2- , attd 3 pentanone, and the like.
to The term "carboxylic ester" means a solvent of formula RCOzR' where R and
R' are
straight or branched alkyl. Carboxylic esters useful in the solvent mixtures
of the present
invention include methyl acetate, ethyl acetate, isobutyl acetate, and the
like.
The term "ether" meats a solvent of formula ROR' where R and R' are straight
or
branched alkyl. Ethers useful in the solvent mixtures of the present invention
include ethyl ether,
i 5 diisopz-opyl ether, methyl tent-butyl ether, and the like.
The term "polar aprotic" refers to solvents which do not contain hydroxy
groups but have
a relatively high dipole moment. Polar aprotic solvents useful in the solvent
mi~etures of the
present invention inclrxde acetonitrile, N,N dimethylforrtamide (bMF),
dimethyl sulfoxide
(DMSO), l,l- dimethoxyethane (DME), hexamethylphosphoric triamide (HMPA), and
the like.
2o By "pharmaceutically acceptable salt" it is meant those salts 'twhich are,
within the scope
of sound medical judgment, suitable for use in contact with the tissues of
humans an,d louver
animals without undue toxicity, irritation, allergic response and the like,
and are commensurate
with a reasonable benefitlrisk ratio. Pharmaceutically acceptable salts are
well Down in the art.
For exatxxple, S. M Berge, et al. describe phartxaaceutically acceptable salts
in detail in .r
25 Pharmaceutical Sciences, 1977, 66: I-I9 . The salts can be prepared in situ
during the final
isolation and purification of the compouzids of the invention, or separately
by reacting the free
base function with a suitable organic acid. Representative acid addition salts
include acetate,
adipate, alginate, ascorbate, aspartate, benzcnesulfonate, benzoate,
bisulfate, borate, butyrate,
CA 02471102 2004-09-23
-5-
camphorate, camphersulfonate, citrate, cyclopentanepropionate, diglueonate,
dodecylsulfate,
ethanesulfonate, fumarate, glucoheptonate, gIycerophosphate, hemisulfate,
heptonate, hexanoate,
hydmbromide, hydrochloride, hydroiodide, 2-hydroxy-ethanesulfonate,
lactobionate, lactate,
lauxate, Iauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-
naphtl~alenesulfonate,
nicotinate, nitrate, oleate, oxalate, palxztitate, pamoate, pectirxate,
persulfate, 3-phenylpropiortate,
phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate,
tartrate, thiocyanate,
toluenesulfonate, undecanoate, valerate salts, and the like Representative
alkali ox alkaline earth
metal salts include sodium, lithium, pota$sium, calcium, magnesium, and the
like, as well as
nontoxic ammonium, quaternary ammonium, and amine rations, including, but not
limited to
to ammonium, tetramethylammonium, tetraethylammonium, methylamine,
dimethylatxtine,
trimethylamine, tTiethylamine, ethylamine, and the lif e,
6-O-methylerythmmycin A is prepared from erytb~omycin A by a variety of
synthetic
routes. In one method, erythromycin A is converted to 2'-O-3'-N
bis(benzyloxycarbonyl)-N
o
t 5 ~zo ~ \
2. OBz
,r
~'a,~ s~,".W
demethylerythromycin A (r).
'The 6-hydroxy group is then txie~thylated by reaction with an alkylating
agent such as
bromomethane or iodometl'tane and a base. Removal of the benzoyl groups by
catalytic
hydrogenation and reductive methylation of the 3' N gives 6-O-
methylerythromycin A. See U.S.
Pat. No. x,331,803.
An alternative synthetic route involves methylatiozt of 6-D-methylerythromycin
A-9-
oxime. 6-O-methylerythromycaz~ A-9-oxim~e is prepared by methods well known
xx~ the art such
CA 02471102 2004-09-23
-6-
as reaction of erythromycin A with hydroxylaixline hydrochloride in the
presence of base, or by
reaction with hydroxylamine in the presence of acid as described in US 1'at.
No. 5,274,085.
Reaction of the oxime with RX wherein R is allyl or benzyl axsd X is halogen
results in formation
of 2'-0,3'-N-diallyl or dibenzylerythromycin A-9-O-allyl or benzyloxime
halide. Methylation of
this quaternary salt as described above, follo'uved by elimination of the R
gt'oups and deaxirnatxon
gives 6-O-nn~ethylerythromycin A. See U.S. Pat. No. 4,670,549.
Methylation of 6-O-methyleryr7~romycin .A. oxime derivatives of foxtnala II,
q~ "2 \ ~ ps
2'
g
I~iW,,. ~~.,~~ a _..v.v0
N0~ ~ O OCHB
O
O O 4.
II
wherein R is alkyl, alkenyl, substituted or tuxsttbstituted benzyl, oxyalkyl,
or substituted
phenylthioallcyl, RZ is benzoyl, and R3 is methyl or benxoyl, followed by
depxotection,
2o deoximation, and reductive methylation when R3 is benzoyl gives 6-O-
methylerythmmycin A.
See U.S. Pat. No. 4,672,109.
A particularly used preparation of 6-O-methylerythromycin A involves
methylation of
the
2
RIO i \ IVY
9 .~,,OH O
...~~0
O
OR3
0
CA 02471102 2004-09-23
oxime derivative III, wherein R' is alkenyl, substituted or unsubstituted
benzyl, or alkoxyalkyl,
R2 is substituted silyl, and R3 is R2 ox H. Removal of the protecting groups
and deoximation is
then accomplished in a single step by treatment with acid to ,give 6-O-
rnethylerythromycin A.
See European Patent Specificatioil 260 938 B1 and U.S. Pat. No. 4,990,602.
A preferred route to 6-O-methylerythromycin A is outlined in Scheme 1.
Erythromycin A, prepared by fermentation of Streptomyces erythreus is oximated
to give oxime
4 wherein R' is alkoxyalkyl. The group Rl may be introduced by reaction of
erythromycin A
with the substituted hydroxylamine R~ONH2, ox by reaction of erythromycin A
with
hydroxylan7~izte hydrochloride in the presence of base, or hydroxylainine in
the presence of acid,
followed by reaction with R1X. The two hydroxy groups are then protected
simultaneously, in.
which RZ or R3 are the same, or sequentially in which R2 and R3 are different.
Particularly useful
protecting groups are substituted silyl groups such as trimethylsilyl, tert
butyldimethylsilyl, tert
z s butyldiphenylsilyl and the like. The protecting groups are then removed
acid the compound is
deoximated to produce 6-O-xxiethyleryrhromycin A. The order of
deprotection/deoximatiori xs not
critical. When the protecting groups are substituted silyl, deprotection and
deo7~iniatiou can be
accomplished in a single step by treatment with acid, for example using formic
acid or sodium
hydrogen sulfite. See U.S, Pat. No. 4,990,602.
zo Scheme 1
a ~' t~r~ R, a
OH 2' di 2'
9 -'~ HD Wa HO O
a ~ ~ HGi.., -~~. 6 .....W
HD..,, w.,,~ "..v .,
Oximation
i.p~~ _ ' !OCH~ HO' ~ O ~.n9
O pi.i ~ pH
O O 11Y .
O ~~
Erychron~yan A
R,O A2 ~ Nr
OH ~ 2'
v o
i"ip,~.. ''
Prpt~n I L Meihyletbn
n.._
OCHa
O
OR3
4-
V
CA 02471102 2004-09-23
_$_
H, O R 2 \ N~ O \ t~l~
OH 2'
9 . .OGH' p z~ '~~ HO O
O NO.
i,, s
doprotedion
ti0~ ~ O
_ OCH9
O d
3 OH
d QR O O 4~
O
6-0-m~thyl~rylhromyoln A
In accordance with the process aspect of the present invention, G-O-
methylerythmmycin
A prepared by any of the methods described above is suspended in the desired
solvent and lxeated
to about the reflux temperature of the solvent. Heating is then continued and
the suspension is
stirred for an amount of time sufficient to dissolve most of the solid,
generally about 10 minutes
to 2 hours. The suspension is then filtered hot. If necessary, the filtrate
may be heated to at or
1s about the reflux ternperaxure of the solvent to form a clear solution. The
filtrate is then. slowly
cooled to ambient temperature with optional further cooling itx az~ ice water
bath. For purposes of
this specification, ambient temperature is from about 20 °C to about 25
°C. Crystalline 6-O-
methylerythromycin A is then isolated, preferably by filtration, and the wet
solid is converted to
6-O-methylerykhromycln A Form I by dry'tug in a vacuum oven at a temperature
of between
2o ambient temperature and about 70 °C, preferably from about 40 to
about 50 °C and a pressure of
between about 2 inches of mercury and atmospheric pressure to remove any
remaining solvent.
In accordance with the aspects of this invention wherein 6-O-
methylerythromycin A is
recrystallized from solvent mi~ctures, 6-O-methylerythromycin A is suspended
in the first solvent
and heated to about the reflux temperature of the solvent. Heating is then
cozttir~ued and the
zs suspension is stirred for an amount of time sufficient to dissolve most of
the solid, generally
about 10 minutes to 2 hours. The suspension. is then filtered hot. The
filtrate may be heated to
reflux to form a clear solution if necessary. A second solvent is then added
to the hot filtrate and
the mixture is cooled slowly to ambient temperature with optional further
cooling in an ice bath.
Representative second solvents include, but are not limited to, hexane,
heptane, octane, acetone,
3o methyl ethyl ketorie, 2-, and 3-pentanone, methyl acetate, ethyl acetate,
isobutyl acetate, ethyl
ether, diisopropyl ether, methyl tart-butyl ether, acetonitrile, N,N
dimethylformamide, dimethyl
CA 02471102 2004-09-23
-9-
sulfoxide, l,l-dimethoxyethane, hexamethylphosphoric trianlide, benzene,
toluezte, and
chlorobenzene. Hydrocarbons of from 5 to 12 carbon atoms are preferred second
solvents. The
most preferred second solvent is heptane. After cooling, 6-O-
methylerythromycin A crystal
Form I is isolated by filtration and drying as described above. The amount of
second solvent
added is dependent on the solubility of the drug in the first solvent and the
second solvent, and
can be readily determined by one of ordinary skill in the art. Typical ratios
fall in the range of
about 1:10 to about 2:1 parts by volume of second solvent. A preferred ratio
of first solvent to
second solvent is 1: I parts by volume.
Preferred solvents for the isolation of 6-O-methylerythromycint A Form I are
ethanol,
to isopropyl acetate, tetrahydrofuran, and isopmpanol,
The most preferred solvent for the isolation of 6-O-rrtethylerythromycin A
Form I is
ethanol.
Pharmaceutical Compositions
The present invention also provides pharmaceutical compositions which comprise
6-0-
15 methylerythromycin A Forth I forzxtulated together with one or more non-
toxic pharmaceutically
acceptable carriers. The pharmaceutical compositions may be specially
formulated for oral
administration in solid or liquid form, for parenteral injection, or for
rectal administration.
The pharmaceutical compositions of this invention can be administered to
humans and
other animals orally, rectally, parenterally, intracisternally,
intravaginally, intrapezitoneally,
20 topically (as by powders, ointments, or drops), bucally, or as an oral or
nasal spray. The term
"parenteral" administration as used herein refers to modes of administration
which include
intravenous, intramuscular, intraperitoneal, intrastemal, subcutaneous and
intraarticular injection
and infusion.
Pharmaceutical compositions of this izwention for parenteral injection
comprise
2s pharmaceutically acceptable sterile aqueous or nonaclueous solutions,
dispersions, suspensions or
emulsions as weh as sterile powders for reconstitution into sterile
iz~jectable solutions ox
dispersions just prior to use, Examples of suitable aqueous and nonaqueous
carriers, diluents,
solvents or vehicles include water, ethanol, polyols (such as glycerol,
propylene glycol,
polyethylene glycol, and the like), and suitable mixtures thereof, vegetable
oils (such as olive
CA 02471102 2004-09-23
-1~-
oil), and injectable organic esters such, as ethyl oleate. Proper fluidity can
be maintained, for
example, by the use of coating materials such as lecithin, by the maintenance
of the required
particle size in the case of dispersions, and by the use of surfactants.
These compositions rnay also contain adjuvants such as preservatives, wetting
agents,
emulsifying agents, anal dispersing agents. Prevention of the action of
microorganisms may be
ensured by the inclusion of various antibacterial and antifungal agents, for
example, paraben,
chlorobutanol, phenol sorbic acid, and the like. It may also be desirable to
include isotonic agents
such as sugars, sodium chloride, and the like. Prolonged absorption of the
injectable
pharmaceutical form may be brought about by the inclusion of agents which
delay absorption
i0 such as aluminum monostearate and gelatin.
In some cases, in order to prolong the effect of the drug, it is desirable to
slow the
absorption of the drug from subcutaneous or intramuscular injection. This may
be accomplished
by the use of a liquid suspension of crystalline or amorphous material with
poor water solubility.
The rate of absorption of the drug then depends upon its rate of dissolution
which, in turn, may
1 s depend upon crystal size and crystalline form. Alternatively, delayed
absorption of a parenterally
administered drug form is accomplished by dissolving or suspending the drug in
an oil vehicle.
Injectable depot forms are made by forming microencapsule matrices of the drug
in
biodegradable polymers such as polylactide-polyglycolide. Depending upon the
ratio of drug to
polymer and the nature of the particular polymer employed, the rate of drug
release can be
2o controlled. Examples of other biodegradable polymers include
poly(orthoesters) and
poly(anhydrides). bepot ixzjectable formulations are also prepared by
entrapping the drug in
liposomes or microemulsxons which are compatible with body tissues.
The injectable formulations can be sterilized, for example, by f ltxation
through a
bacterial retaining filter, or by incozporating sterilizing agents in the form
of sterile solid
zs compositioxis which can be dissolved or dispersed in sterile water or other
sterile injectable
medium just prior to use.
Solid dosage forms for oral administration include capsules, tablets, pills,
powders, and
granules. In such solid dosage forms, the active compound is mixed with at
least one inert,
CA 02471102 2004-09-23
-11-
pharmaceutically acceptable excipient or carrier such as sodium citrate or
dicalcium phosphate
and/or
(a) fillers or extenders such as starches, lactose, sucrose, glucose,
mannitol, and
silicic acid,
(b) binders such as, for example, carboxymethylcellulose, alginates, gelatin,
polyvinylpyrrolidone, sucrose, and acacia,
(c) humectants such as glycerol,
(d) disintegrating agents such as agar-agar, calcium carbonate, potato or
tapioca
starch, alginic acid, certain silicates, arid sodium carbonate,
(e) solution retarding agents such as paraffin,
(f) absorption accelerators such as quaternary ammonium compounds,
(g) wetting agents such as, for example, cetyl alcohol and glycerol
monostearate,
(h) absorbents such as kaolin azxd bentonite clay, and
(i) lubricants such as talc, calcium stearate, magnesiuzx~ stearate, solid
polyethylene
I5 glycols, sodium lauryl sulfate, and mixtures thereof.
In the case of capsules, tablets and pills, the dosage form may also comprise
buffering agents.
Solid compositions of a similar type may also be employed as ~llezs in soft
and hard-
filled gelatin capsules using such excipients as lactose or mills sugar as
well as high ntiolecular
weight polyethylene glycols and the like.
2o The solid dosage forms of tablets, dragees, capsules, pills, and granules
can be prepared
with coatings and shells such as enteric coatings and other coatings well
known in the
pharmaceutical formulating art. They may optionally contain opacifying agents
arid can also be
of a composition that they release the active ingredients) only, or
preferentially, in a certain part
of the intestinal tract, optionally, in a delayed manner. Examples of
embedding compositions
25 which earl be used include polymeric substances and waxes.
CA 02471102 2004-09-23
e.:
~ -12-
The active compounds can also ba in micro-encapsulated form, if approp~ciate,
with one
or more of the above-mentioned excipients.
~ .;
Liquid dosage forms for oral administration include pharmaceutically
acceptable
emulsions, solutioxis, suspensions, syrups and elixirs. In addition to the
active compounds, the
liquid dosage forms may contain inert diluents commonly used in the art such
as, for example,
water or other solvents, solubilizing agents and emulsifiers such as ethyl
alcohol, isopropyl
alcohol, ethyl carbonate, ethyl acetate, ben2yl alcohol, benzyl benzoate,
propylene glycol, 1,3-
. ,.
butylene glycol, dzmethyl formamide, oils (in particular, cottonseed,
groundnut, corn, germ,
;, ~.,
olive, castor, and sesame oils), glycerol, tetrahydmfurfuryl alcohol,
polyethylene glycols and
:,',.. 10 fatty acid esters of sorbitan, and mixtures thereof.
Resides inert diluents, the oral compositions can also include adjuvants such
as wetting
agents, emulsifying and suspending agents, sweetening, flavoring, arid
perfuming agents.
Suspensions, in addition tv the active compounds, may contain suspending
agents as, for
,:
example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and
sorbitan esters,
:.,
;'y.,, 15 microcrystalline cellulose, aluminum metahydroxide, bentonite, agar
agar, and tragacantb, and
,' ~i ~ mixtures thereof.
Compositions far rectal or vaginal administration are preferably suppositories
which can
l'' ' be prepared by mixing the compounds of this invention with suitable non-
irritating excipients or
carriers such as cocoa butter, polyethylene glycol or a suppository wax which
are solid at room
~:a; 20 temperature but liquid at body temperature and therefore melt in the
rectum or vaginal cavity and
release the active compound.
Compounds of the present invention can also be administered in the form of
liposomes.
As is lrnown in the art, liposomes are generally derived from phospholipids or
other lipid
substances. Liposomes are formed by mono- or multi-lamellar hydrated liquid
crystals that are
25 dispersed in an aqueous medium. Any non-toxic, physiologically acceptable
and metabolizable
lipid capable of forming liposomes can be used. The present compositions in
liposome form can
;'~ contain, in addition to a compound of the present invention, stabilizers,
preservatives, excipients,
~_., ~~ .
. ,..
CA 02471102 2004-09-23
'~ s
-13-
and the like. The preferred lipids are the phospholipids and the phosphatidyl
cholines (lecithins),
both natural and synthetic.
Methods to fornn liposomes are known in the art. See, fox exanxple, Prescott,
Ed.,
Methods in Cell Bioloav, Volume XIV, Academic Press, New York, N.Y. (197, p.
33 et seq.
Dosage forms for topical administration of a compound of this invention
include
'. ; powders, sprays, ointments and inhalants, The active compound is mixed
under sterile conditions
with a pharmaceutically acceptable carrier and any needed preservatives,
buffers, or propellants
' which may be required. Opthalmic fomaulations, eye ointments, powders and
solutions are also
;vl,; contemplated as being within the scope of this invention.
1 o Actual dosage levels of active ingredients in the pharmaceutical
compositions of this
invention may be varied so as to obtain an amount of the active compounds)
that is effective to
achieve the desired therapeutic response for a particular patient,
composition, and mode of
administration. The selected dosage level will depend upon the activity of the
particular
compound, the route of administration, the severity of the coxidition being
treated, and the
condition and prior medical history of the patient being treated. However, it
is within the skill of
the art to start doses of the compound at levels lower than required to
achieve the desired
.. . therapeutic effect and to gradually increase the dosage until the desired
effect is achieved.
Generally dosage levels of about 1 to about 1000, more preferably of about 5
to about
200 mg of 6-O-methylerythromycin A Form I per kilogram of body weight per day
are
', 2o administered to a mammalian patient. If desired, the effective daily
dose may be divided into
multiple doses for purposes of administration, e.g. two to four separate doses
per day.
The following Examples are provided to enable one skilled in the art to
practice the
invention a»d are merely illustrative of the invention. They should not be
read as limiting the
scope of the invention as defined in the claims.
,,,, .
E~tample 1
Preparation of 6-O-methyle omycin Form I
i'i . CA 02471102 2004-09-23
~-i
. ~ -14-
6-O-metlzylerythromycin A was prepared from erythromycin A by oximation of the
C-9
,.. ~,
carbonyl, protection of the C-2' axtd C-4" hydroxy groups, methylation of the
C-6 hydroxy group,
. ; , deoximation and removal of the protecting groups, and recrystallization
from ethanol according
to the method of U.S. Pat No, 4,990,602. The material obtained from the
recrystallization was
dried in a vacuum oven (40-45 °C, 4-8 in. Hg) to give 6-O-
methylerythromycin A Form I.
6-O-methylerythromycin A Form I is characterized by its infrared spectrum, the
differential scanning calorimetric (DSC) thermogram and the powder x-ray
difhaction pattern.
'' ~ r
,y The differential scanning calorimetric thetxoogram is obtained by methods
known in the art and
is illustrated in Figure lc. In Figure lc, an exothermic transition at 132.2
°C can be seen, which is
,. ;',
' 10 believed to be due to a phase transition. An endothermic peak at 223.4
°C, which may be due to
"
melting, can also be seen. Another endothermic peak at 283.3 °C
followed by an exothermic
peak at 306.9 °C may be due to decomposition. After the DSC scant the
color of the sample was
i .
:,' ; ' black.
"; The powder x-ray diffraction pattern is obtained by the methods lrnown in
the art. Figure
1 a illustrates the powder x-ray difr'raction pattern. The 2-theta angle
positions in the powder x-
°'.v
ray diffraction pattezzt of 6-O-methylerythrotnycin A Form I are
5.16°f0.2, 6.68°t0,2,
10.20°f0.2, 12.28°~0.2, 14.20°~0.2, 15.40°~0.2.
15.72°~0.2, and 16.36°~0.2.
Example Z
Conversion of 6-O-methyIerythromycin Form I Crystals to Form II Crystals
6-O-t~nethylerythromycin A Form I crystals (0.40 g), prepared as in Example 1,
were
y i placed in a vial and heated in the vacuum oven (4-9 in Hg, 100-110
°C) for 18 hours to give 6-O-
ttaethyler)rthromycin A Form n crystals. 6-O-methylerythromycin A Form II
melts at 223.4 °C.
In the differential scattttiztg calorimetric therraogram of 6-D-
methylerythromycin A Form II there
can be seen an endothermic peak at 283.3 °C which may be due to
decomposition. After the DSC
scan the color of the sample was black, The 2-theta angle positions in the
powder x-ray
'-, ; diffraction pattern of 6-O-methyierythromycin A Form a are
8.52°~0.2, 9.48°~0.2, 10.84°t0.2,
11.48°~0.2, 11.88°t10.2, 12.36°~0.2, 13.72°f10.2,
14.12°~0.2, 15.16°f0.2. 16.48°t0.2,
16.92°f0.2, 17.32°t0.2, 18.08°~0.2, 18.40°t0.2,
19.04°t0.2, 19,88°~0.2, and 20.48°f0.2.
.v.., ~ .
- CA 02471102 2004-09-23
a ' -15-
~,, r ;
:;; . Example 3
isolation of 6-O-xnethyler~rthromycin Form I bar Recrvstallization
.y
i Recrystallization from 'fetrahydrofuran
A ;txxixture of 6-O-methyleryyhromycin A (20 g), prepared as described in
Example 1, in
. ;.
S tetrahydrofuran (100 mL) was warmed to reflex and stirred for 15 minutes.
The hot solution was
~xltered to remove traces of insoluble material and cooled to ambient
temperature. No
crystallization occurred so 10 g of 6-O-methylerythromyciza A was added to the
solution and the
suspension was again heated to reflex, hot filtered, and cooled in an ice
bath. The resulting solid
was collected by filtratiorA and dried in the vacuum oven (40-45 °C, 4-
8 in. Hg) to give 6-O-
~ o methylerythromycin A Form I ( 16.74 g).
.a
:i
Recrystallization from Isopropyl Alcohol
i A mixture of 6-O-methylerythromycin A (15 g), prepared as described ixi
Example 1, and
v isopropyl alcohol (100 mL) was warmed to reflex and heated for 20 minutes.
The hot solution
was filtered to remove traces of insoluble material. The filtrate was
transferred to another flask
:.;
15 along with a 50 zn,L isopropanol rinse, and the solution was again heated
to reflex. The clear
solution was then cooled slowly to ambient temperature and left standing for
seven hours. The
j;~', resulting solid was collected by filtration and dried in the vacuum oven
(40-45 °C, 4-8 in. Hg) to
give 6-D-methylerythromycin A Form I (13.3g).
,,, ;
Recrystallixation from Isopropyl Acetate
2o A mixture of 6-O-methylerythroxnycin A (10 g), prepared as described in
Example 1, and
isopropyl acetate (100 mL) was warmed to 73 °C. The hot solution was
filtered to remove traces
:.;
..; of insoluble material. The clear solution was then cooled slowly to
ambient temperature, The
',.i , resulting solid was collected by filtration and dried ip the vacuum
oven (40-45 °C, 4-8 in. Hg) to
give 6-O-methylerythromycin A Form I (3.6 g).
""
.:; ,
25 RecrystalIization from Isopropyl Acetate-Heptane
A nn~ixture of 6-O-methylerythromycin A (10 g), prepared as described in
Example 1, and
isopropyl acetate (100 mL) was warmed to reflex. A small amount of insoluble
material was
-;; ,.
, CA 02471102 2004-09-23
-16-
removed by filtration and the filtrate was transferred to another vessel. The
filter flask was rinsed
with isopz'opyl acetate (5 mL) and the filtrate and rinse were combined and
heated to reflex. To
the resulting clear solution was added heptane (100 mL) and the clear solution
was cooled to
ambient temperature over 1.5 hours during which time a precipitate forrued.
The solid was
collects by filtration and dried overnight in the vacuum oven (45-50
°C, 4-8 in. Hp~ to give 6-
O-methylerytbromycizt A Fomn I (7.0 g).
Recrystallization from rsoprapyl Acetate N,N dimethylformamlde
,,, .
;.
A mixture of 6-O-xnethylerythromycin A (12 g), prepared as described i»
Example 1, and
isopropyl acetate (100 tnL) was warmed to reflex. A small amount of insoluble
material was
v to removed by filtration and the filtrate was transferred to another vessel.
The filtrate was heated to
',
reflex and N,N dimethylformamide (30 mI,) was added. The clear solution was
cooled to
ambient temperature over 1.5 hours during which time a precipitate formed. The
solid was
collected by fiiltration and dried overnight in the vacuum oven (49-50
°C, 4-8 in. Hg) to give 6-
O-rnethylerythron7,ycin A Form I (6.4 g).
Recrystallization from Tetrahydrofuran-Hcptane
To a clear solution of 6-O-methylerythromycin A (10 g), prepared as described
in
F,~cample 1, in teh'ahydrofuran (75 mL) was added heptane (150 mL). The
resulting cloudy
",; solution was heated to 71.5 °C at which point it turned clear. The
mixture was cooled to ambient
temperature over 2 hours, a~ad then was cooled in an ice-water bath for 0.5
hours. The resulting
2o solid was filtered and dried in the vacuum oven (45-50 °C, 3-4 in.
Hg) for four days to give 6-O-
methylerythromycin A Form I (0.50 g).
Recrystallization from Ethanol-Heptane
a v - A mixture of 6-O-methylerythromycin A (10 g), Prepared as described in
Example 1, and
ethanol (100 mL) was warmed to reflex, A small amount of insoluble material
was removed by
filtration and the filtrate was transferred to another vessel. The filter
flask was rinsed with
ethanol (20 mL) and the filtrate and rinse were combined and heated at 78
°C until a clear
solution was obtained. To the clear solution was added heptane (100 mL) and
the clear solution
was cooled slowly to ambient temperature and stirred for four days. The
resulting solid was
. CA 02471102 2004-09-23
. -17-
:.;
collected by filtration and dried in the vacuum oven (45-50 °C, 4-8 in.
Hg) to givc 6-O-
methylerythromycin A Form I (4.5 g).
Recrystallnxation from lsopxopanol-Heptane
A mixture of 6-O-methylerythromycin A (4.0 g), prepared as described in
Example 1,
. 5 and isopropataol (50 mL) was warmed to reflux. Heptane (50 mL) was added
and the solution
was cooled slowly to ant~bient temperature and then was cooled in ~r ice-water
bath. T'he
resulting solids were collected by filtration and dried in the vacuum oven (4-
8 in. Hg) to give
6-O-methylerythromycin A Form I (3.6 g).
Example 4
Dissolution Rates o~6-O-methylerythromycin Forms I and II
Dissolution studies were carried out at 60 rpm in 300 mL of 0.05 M phosphate
buffer at
37°C using a constant surface area (13/32" diaxneter) drug compact.
Aliquots were removed
:,
periodically and assayed directly by HPLC (Scm x 4.6mm 3p. ODS 2 "Little
Champ" (Regis)
,, column; 50:50 acetonatrile-0.05 M pH 4.0 phosphate buffer mobile phase; 1.0
mIJmin flow rate).
15 As shown in Table 1, 6-O-methylerythromycin A Foam I has an intrinsic rate
of dissolution
about three times greater than Form II.
Table 1
' Intrinsic
Dissolution
Rates
of 6-O-methylerythromycin
A forms
I and
II
Crystal Form Dissolution Rate f S.D.
. (N.g/min/cm2)
I 636 t 2.5
v II ~ 203 ~ 14
2o The foregoing examples are presented fot' purposes of illustration and are
not intended to
limit the scope of the invention. Variations and changes which are obvious to
one skilled in the
art are intended to be within the scope and nature of the invention as defined
in the appended
claims.
