SODIUM CEFAMANDOLE CRYSTALLINE FORMS

SODIUM CEFAMANDOLE SOUS FORME CRISTALLISEE

English Abstract

Abstract of the Disclosure
A novel crystalline anhydrate of sodium 7-
(D-2-hydroxy-2-phenylacetamido)-3-(1-methyl-1H-tetrazole-
5-ylthiomethyl)-3-cephem-4-carboxylate is described herein.
The novel anhydrate is prepared by removing methanol or
monohydrate solvate under reduced pressure. The novel
anhydrate is an antibiotic.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A process for preparing the crystalline
anhydrate of sodium 7-(D-2-hydroxy-2-phenylacetamido)-
3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-cephem-4-
carboxylate which has the following X-ray powder diffraction
pattern obtained with nickel filtered copper radiation of
.lambda.1,5405.ANG. wherein .lambda. represents wave length, d represents
the interplanar spacing and I/I1 represents the relative
intensity:
<IMG>
14

<IMG>
which comprises removing the solvent from a
crystalline sodium 7-(D-2-hydroxy-2-phenylacetamido)-
3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-cephem-4-
carboxylate solvate under reduced pressure.
2. The process of Claim 1 for preparing the
crystalline anhydrate of sodium 7-(D-2-hydroxy-2-phenyl-
acetamido)-3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-
cephem-4-carboxylate which comprises subjecting the crys-
talline methanol solvate of sodium 7-(D-2-hydroxy-2-
phenylacetamido)-3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-
3-cephem-4-carboxylate to reduced pressure at a temperature
between about 25° and 45°C.
3. The process of Claim 1 for preparing the
crystalline anhydrate of sodium 7-(D-2-hydroxy-2-phenyl-
acetamido)-3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-
cephem-4-carboxylate which comprises subjecting the crys-
talline monohydrate of sodium 7-(D-7-hydroxy-2-phenyl-
acetamido)-3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-
cephem-4-carboxylate to reduced pressure at a temperature
between about 45° and 50°C.
4. The crystalline anhydrate of sodium 7-(D-2-
hydroxy-2-phenylacetamido)-3-(1-methyl-1H-tetrazole-5-
ylthiomethyl)-3-cephem-4-carboxylate which has the following
x-ray powder diffraction pattern obtained with nickel

filtered copper radiation of .lambda.1,5405.ANG. wherein .lambda. represents
wave length, d represents the interplanar spacing and I/I1
represents the relative intensity:
<IMG>
16

<IMG>
whenever prepared by the process of claim 1, 2 or 3, or by
an obvious chemical equivalent thereof.
17

Description

SODIUM CEFAMANDOLE CRYSTALLINE FORMS
The cephalosporin antibiotic 7-(D-2-hydroxy-2-
phenylacetamido)-3-(1-methyl-lH-tetrazole-5-ylthiomethyl)-
3-cephem-4-carboxylic acid represented by the structural
formula
~ ~o CH-C-N~
OH o~ CH2-S~
OOH I .
CH
is described by Ryan in U.S. Patent No. 3,641,021. This
antibiotic, referred to herein as cefamandole, is a potent
broad spectrum parenteral antibiotic with excellent activity
against infecti.ous microorganisms of the gram-negative type.
Although cefamandole can be readily prepared, it has been
difficult to obtaln a pharmaceutically acceptable salt of
cefamandole in a crystalline form of sufficient stability
and purity suitable for parenteral administration. ~ -
Extensive development work on the antibiotic has
afforded the O-formyl ester of cefamandole sodium salt in
the gamma crystalline form as described in ~elgian Patent
840179. This crystalline form of the O-formyl derivative of~-
cefamandole sodium is suitable for parenteral administration;
however, it is best administered when formulated with a mild
base such as sodium carbonate. Such formulations are described ~ `
in U.S. Patent 3,928,592 issued December 23, 1975.
A stable, crystalline form of sodium cefamandole
suitable for bulk preparation and administxation would avoid
the necessity of preparlng the O-formyl derivative form and
3~ would thus simplify the production of the antibiotic.
X-4625 -2-
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.
" ' ~ '., ` ' ` t ' ' ~ ' '

This Lnvention, in one aspec-t, provides a crystalline
anhydrate of sodium cefamandole which is readily prepared and
which possesses the stability characteristics desirable in
formulations of the antibiotic.
This invention also provides a crystalline methanolate
and, in a further aspect, a crystalline monohydrate of sodium
cefamandole. These forms are useful as intermediate crystalline _
structures in the preparation of the anhydrate crystals of
sodium cefamandole.
The crystalline anhydrate of sodium csfamandole
is prepared by removing the solvent from a crystalline
sodium cefamandole solvate under reduced pressure.
The crystalline anhydrate of sodium cefamandole is
a white microcrystalline solid which is best characteri~ed
by its x-ray powder diffraction pattern shown below. The
diffraction pattern was obtained with nickel filtered copper
raldiation (Cu:Ni) of wave length ~ = l.5405A. The inter-
planar spacings are in the column headed by "d" and the
relative intensities in the column headed "I/I~
Spacing Relative Intensity
d IjI
14.24 .61
12.70 .22
8.14 .15
7.92 .23 -
7.25 .71
6.60 .lS
6.43 .30
,
5133 .13
;
X-46~5 -3_
.. ...... .
~ ' ' ' '' ''' ' .

5 0~ .12
4.83 55
4~29 .29
~.17 .15
4.02 .26
3.64 .12
3.60 .13
3.58 . .12
3.50 .05
3.~2 .06
3.28 .07
3.20 .08
3.14 .06
2.96 .09
2.~37 .21
2.80 .06
2.72 .15
2.67 .08
2.57 07
2.52 .04
2.41 .12
2.29 . .15
.: .~ .,
Stability studies carried out thus far on the
.
crystalline anhydrate demonstrate substantially no loss in
either antibiotic activity or in crystallinity when the salt
: :
is maintained for one week at 60C.
This invention also provides the crystalline :
: ~ .
methanolate and monohydrate forms of sodium cefamandole.
Both of these-novel forms can be used to prepare the crys~
talline anhydrate as discussed hereinafter.
X-4625 _4~
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The crystalline methanolate, alternatively re-
ferred to herein as ths methanol solvate, is characterized
by its x-ray powder diffraction pattern shown below. The
pattern was obtained using nickel filtered copper radiation
(Cu:Ni) of wave length ~1.5405A to calculate the interplanar
spacings and the relative intensities.
SpacingRelative Intensity
d I/I
15.22 .06
1~.24 1.00 ~ :
12.99 .25 `
8.75 .18
7.92 .19
7.65 45 ;
7.16 .46 ~`:
6.93 .25
6.62 .18
5.48 .15 ~ ~
5.30 .07 `:
5.11 .26
4.98 .47
4.79 .40 ;.
4.64 . .19 .
4.22 .08
4.15 ` 07 ;-
3.76 .11
3.89 .28 :
3.70 .18
3.58 .19 ;~ :
3.49 .~2 ~ ::
X-~625 -S- ~
: . . , ~ : . ; - .:

3.35 .13
3.12 .09
2.93 .06
2.89 .17
2.79 .10
2.76 .08
2.66 .09
2.56 .07
The methanolate form contains about 6.0 percent by
weight of methanol which corresponds to a mole ratio of
methanol to sodium cefamandole of l:l.
The crystalline methanol solvate can be prepared
by crystallizing substantially pure amorphous sodium
cefamandole from methyl alcohol. Alternatively, the
methanolate ca~ be prepared with cefamandole acid by con-
verting the acid in methyl alcohol to sodium cefamandole
with the sodium salt of a weak acid. The sodium cefamandole ~
precipitates from solution as the crystalline methanolate. `
Salts of weak acids which can be usecl include, for example, ~-
sodium acetate, sodium propionate, sodium 2-ethylhexanoate,
and like sodium salts of weak carboxylic acids which are
soluble in methanol.
The present invention, in one aspectr therefore,
resides in a process or preparing the above-defined
crystalline methanolate of sodium cefamandole which comprises ~;
carrying out one of the following procedures:

(a) conversion of 7-(D-2-hydroxy-2-phenylacet~mide)-
3-(l-methyl-lH-tetrazole-5-ylthiomethyl)-3-Cephem-4-carboxylate
acid with methanol and the sodium salt of a weak acid at a
temperature between about 0 and 50C., or
(b) conversion of amorphous sodium 7-(D-2-hydroxy- -
2-phenylacetamido)-3-(l-methyl-lH-tetrazole-5-yl~hiomethyl)-3-
cephem-4-carboxylate with methanol at a temperature between
about 0 and 50~C.; or
(c) conversion of the crystalline anhydrate of
sodium 7-(D-2-hydroxy-2-phenylacet~m;do)-3-(l-methyl-l~-
tetrazole-5-ylthiomethyl~-3-cephem-4-carboxylate with dry
methanol; or
(d) conversion of the crystalline monohydrate of
socLium 7-(D-~-hydroxy-2-phenylacetamido)-3-(l-methyl-lH-
tetrazole--5-ylt~iomethyl)-3-cephem-4-carboxylate with dry
methanol.
The crystalline methanolate form of sodium cefamandole,
and the process for its preparation is also described, and
claimed in Canadian Patent Application No. 266,112, filed
November 19, 1976,of which the present application is a
divisional.
The methanol solvate crystalline form is preferably
prepared with substantially pure cefamandole in the free acid
form as follows. The Cefamandole acid is dissolved in methyl
alcohol, and a solution of excess sodium acetate in methyl
alcohol is added to the solution. The solution of sodium
acetate is added slowly to avoid gel formation and addition
is halted when the pH reaches about
-~a-

6. The solution thus obtained (crystallization solution) is
allowed to stand to complete crystallization. The crystals
of methanol solvate are filtered and washed with a suitable
dry organic solvent, for example ethanol or diethyl ether,
and then are allowed to dry.
The crystallization procedure or the methanol
solvate can be carried out at a temperature between about ~,
0C. and 50C. The preferred temperature range of crystal- ''
lization is between 15 and 40C. Over the preferred tem-
perature range yields of the methanolate crystalline form
are generally between about 90 and 95 percent. At tempera- `
tures much above 40C. the yields are usually lower. For
example, at a crystallization temperature of about 50C.,
yields of methanolate are about 60 percent. ;
The crystallization of the methanol solvate is
preferably carried,out under substantially anhydrous con-
ditions. Although trace or minor amounts of water in'the
crystallization solution have no deleterious effect on the '~ -
yields of methanolate crystals, larger amounts can result in
the foxmation of hydrated crystalline forms along with the
methanol solvate form. Accordingly, for best results the
crystallization is carried out with dry methanol and with
anhydrous sodium acetate. Reagent grade methanol and an-
hydrous sodium acetate are also preferred over less pure
grades.
The methanol solvate is obtained in highest yields
from a concentrated crystallization solution. Therefore,
concentrated solutions of cefamandole free acid in methanol ~,
.~ ~
and of anhydrous sodium acetate in methanol are used to form
X-4625 -7- ~
.:
:

the concentrated crystallization solution of sodium cefaman-
dole. A suitable concentration of cefamandole acid in
methanol is about one gram of the antibio-tic acid per 2-3
ml. of methanol. A concentrated solution of anhydrous
sodium acetate in methanol containing about 1 g. of an-
hydrous sodium acetate per 12 ml. of methanol can be con-
veniently prepared at room temperature as follows. Excess
anhydrous sodium acetate is stirred in methanol for several
minutes and the undissolved salt is filtered. The filtrate -
can then be used to form the crystallization solution with
the methanol solution of cefamandole free acid.
Methyl alcohol is unique in its ability to form a
crystalline solvate of sodium cefamandole. Attempts to
prepare crystalline forms of sodium cefamandole with other
alcohols have led to the formation of a rphous salt. For
example, when in the above described preparation for the
ethanolate, methyl alcohol is replaced with ethyl alcohol,
amorphous sodium cefamandole is obtained rather than an
ethanol solvate.
The methanol solvate is the precursor crystalline
form for both the anhydrate and monohydrate crystalline
forms described herein. The methanol of crystallization of
the methanolate form can be removed in vacuo to provide the
anhydrate crystalline form or, alternatively, the methanol
of crystallization can be displaced by water to form the
crystalline monohydrate form.
The crystalline monohydrate of sodium cefamandole
contains about 4 percent by weight of water which corre-
sponds to a ratlo of water to sodium cefamandole of 1:1.
-~
X-4625 -8-
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4~
The monohydrate crystalline structure differs from that ofboth the anhydrate and the methanolate. The x-ray powder
diffraction pattern of the monohydrate is shown below.
Again, nickel filtered copper radiation of wave length
~1.5405A was used.
SpacingRelative Intensity --
d I/Il
_
13.79 57
12.23 .40
8.23 .12
7.52 09
7.21 40
7.02 .60
6.67 .15
6.].9 .25
5.09 .10
4.~4 42
4.70 33
4.15 .37
3-99 .26
3.84 .08
3.76 .09
3.65 .12
3.55 .10
.:
3.40 .08
3.25 .10
3 07 .11
2.92 .06
2.76 .16
2.65 .11
X-4625 _9_
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;~ ..1~,',
~ ~ ' .;
,. . - .

~8'3l~!L~
2.6205
2.4915
2.4l.OS
2.36.07
2.~3.11
The monohydrate is prepared with the above-
described methanol solvate by allowing water to displace the
methanol of crystallization in the methanolate crystals.
The preparation of the monohydrate is carried out by ex-
/~ posing the methanolate crystals to moist air. The displace-
ment of methanol with water occurs at a convenient rate at a
relative humidity of between about 40 and 60 percent at a
temperature between about 20 and 30C. The preferred
conditions are 50 percent relative humidity at 25C. The
preparation of the monohydrate crystalline form is con-
ve!niently carried out in this manner in a humidity chamber.
This aspect of the inven~ion is also described, and ~ -~
is claimed, in Canadian Application ~o. 344,208, filed January 22, 1980, a
divisional of Canadian Application No. 266,112.
~ The monohydrate is less stable than the anhydrate.
It becomes discolored and loses some antibiotic activity as
well as undergoing crystalline disfiguration in the standard
stability test carried out at 60C. for one week. ~;
The previously described crystalline anhydrate of
~odium cefamandole can be prepared with either the monohy-
drate or preferably with the methanol solvate. The water of ~
crystallization of the monohydrate or the methanol of ~ ~;
crystalli~ation of the methanol solvate are removed under
reduced pressure to provide the anhydrate crystalline form.
The conversion of the methanol solvate to the
anhydrate crystalline form is carried out under vacuum at a `~
temperature between about 25 and 45C. and preferably at
a~out 40C.
- - . - - . , , .
- ., . ; , , . .- .

The monohydrate crystalline Eorm can be dehydrated
under vacuum at a temperature between about 45 and 50C. to
form the anhydrate. Preferably, a drying agen-t is placed in
the vacuum oven to increase the rate of anhydrate formation.
The monohydrate will lose water at room tempera-
ture at 0 percent relative humidity; however, the rate is
much slower than when dehydration is carried out as de-
scribed above.
The anhydrate form of sodium cefamandole will
rehydrate to the monohyclrate crystalline form if exposed to
moist air. For example, at a relative humidity of about 55
percent at about 25C., the anhydrate absorbs about 40
percent by weight of water in less than an hour. Accord-
ingly, the anhydrate crystalline form is stored prior to use
in sealed containers or in a dry atmosphere to prevent the
formation of the less stable monohydrate form.
The anhydrate or thè monohydrate can be converted
to the methanolate crystalline form by crystallization from
dry methyl alcohol. ~
The conversion of -the three crystalline forms of ~;
sodium cefamandole into one another clS discussed above is
illustrated by the following triangular diagram.
Sodium Cefamando~e CH30H
CH30H ~ -CH30U C 30H ~ H~0
Anhydrate \ - Monohydrate
_H20
'' '~': ' ' '
;~
X-462S -11-
"' ':
,; ' ~'
-- - ... . - .. ~, ~ ,

The crystalline anhydrate can be stored in bulk
form in closed containers for subsequent formulation.
Alternatively, it can be prepared in unit dosage~form in
sealed ampoules for parenteral administration in the treat-
ment of infectious diseases. The crystalline monohydrate
and the crystalline methanol solvate are intermediate
crystalline forms useful for preparing the anhydrate form.
The following examples are provided to further
illustrate the present invention.
Example 1
Sodium Cefamandole Methanolate
To a solution of 100 g. of cefamandole acid in
approximately 200 ml. of methyl alcohol was slowly added a
solution of 25 g. of anhydrous sodium acetate in 300 ml. of
methyl alcohol until the pH of the solution reached pH 6.
The solution was allowed to stand at room temperature until
crystallization of the methanolate crystalline form was
complete. The crystals were harvested by filtration through ~`
a Buchner funnel and were washed with dry ethyl alcohol and
with diethyl ether.
Example 2
Sodium Cefamandole Anhydrate
A solution of cefamandole acid in methanol was
prepared by dissolving 4.0 kg. of cefamandole acid in 8.8 1.
of methyl alcohol with stirring. To the solution was added
with vigorous stirring a solution of 0.98 kg. of anhydrous
sodium acetate in 9.0 1. of m~thyl alcohol. The rate of
addition of the sodium acetate solution was about 0.25
liters per minute. After addition was completed, the crystal
~-4625 -12-

~U~ L'lL~
slurry was stirred for one hour. The crystals of methanol
solvate were then harvested on a Buchner funnel and were
washed with a mixture of one liter of methanol and one liter
of ethanol on the filter. The washed crystals were trans-
ferred to drying pans and spread in a thin layer. The
drying pans were placed in a Stokes oven and the crystals
dried under vacuum (28 inches Hg.) at a temperature of about
40C. The dried crystals of anhydrate were transferred to
amber glass jars which were sealed for storage.
Example 3
Sodium Cefamandole Monohydrate
Ten grams of sodium cefamandole methanolate crystals,
prepared as described by Example l, were exposed at room
temperature to approximately a 50 ~ lO percent relative
humidity for about 16 hours to provide 9.8 g. (quantitative
yield) of sodium cefamandole monohydrate crystals.
' `~'': '' "
'~'' ~ . :'
~'''; '` ` ' '
X-4625 - -13~