Note: Descriptions are shown in the official language in which they were submitted.
~;)7~17~(~
Essentially crystalline cephalothin s~dium for
parenteral administration is prepared by a freeze-drying
process wherein a (Cl-C3 alcohol or acetone)-water solution
of cephalothin sodium containing from 2 to 10 percent of a
Cl-C3 alcohol or acetone by volume is chilled from room
temperature to -20C., or below, preferably -40C. over a
1-3 hour period and then warmed to from -3C. to -10C. and
held for 3 hours or more, then cooled to -20C, or below,
preferably -40C., before subjecting said frozen solution to
a high vacuum and a moderate amount of heat to sublime the
frozen solvent therefrom. The resulting powder dissolves
rapidly in acceptable pharmaceutical diluents. Alternatively,
from 2 to 5 percent by weight of sodlum bicarbonate, related
to the amount of cephalothin sodium present, is added to the
solution before freeze-drying.
Freeze-drying is an old and often used process for
removing a solvent from a solute. It provides a method for
removing a solvent without damaging heat labile solutes.
Antibiotics and other pharmaceuticals, and foods, partic-
ularly instant coffee, have been prepared by this method formany years. Ordinarily, a solution from which it is desired
to reco~er the solute is frozen solid and then subjected to
a high vacuum, and the temperature of the environment is
- raised to provide the units of heat absorbed in the sublimation
of the frozen solvent. The temperature of the environment
is kept below that which would result in the meltdown of the
frozen solution. In practice, the temperature of the
environment is coordinated with the vacuum to produce the
highest reasonable sublimation rate, avoiding a melting of
the frozen mass.
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Water i~ the solvent generally u~ilized in a
freeze-drying process. Other solvents or combinations
thereof can be employed but are limited to those which
become solid in the range of temperatures which can be
employed practically in the process and which will sublime
under vacuum.
In freeze-drying antibiotics and other pharma-
ceuticals it has been the practice to follow the classic
process outlined above; to wit, prepare solution, freeze to
; 10 solid, subject to high vacuum, add heat, sublime solvent.
However, when such a conventional procedure is followed, the
process involving cephalothin sodium requires A cycle time
of more than 24 hours to achieve a stable crystalline
product.
The cephalothin sodium involved in this invention
can be recovered from organic solvents, such as those iden-
tified above, in an essentially crystalline state.
However, such crystalline cephalothin sodium poses
other problems. For example, there is no effective way
known to sterilize the crystals of cephalothin sodium
recovered from organic solvents so the entire crystalliza-
tion process must be carried out in an aseptic environment.
In the large and extensive process required to sterilely
crystallize cephalothin sodium there are many opportunities
for the admittance of contaminating foreign materials.
Further, no one has yet developed an apparatus for filling
dry material into an ampoule which will measure the material
going into each ampoule with as good a consistency and
precision as can be routinely achieved with liquid filling
equipment.
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- United States Patent No. 4,02g,655 describes a
process which embodies a procedure that includes a very
rapid cooling of an aqueous solution to nucleate the
cephalothin sodium, among other cephalosporins, during the
interval that the freezing takes place. Such nucleation
crystallizes the bulk of the cephalothin sodium from the
solution immediately prior to the solidification of the
water. Consequently, when the sublimation procedure is
initiated the cephalothin sodium already exists as crystals
and does not depend on the crystallization to take place as
the solvent is removed. rrhe solvent is sublimed away and
the cephalothin sodium remains behind. '
While the above process provides stable sterile ~;
crystalline cephalothin sodium for parenteral administration,
the process requires more than 24 hours for the completion
of one cycle. Consequently, the scheduling of the use of
the ~reeze-drying equipment and the work schedules of the
personnel is unsatisfactory becau~e of the irregularity of
the operation. Following the teachings of the prior art
X;~ requires a 28 to 36 hour cycle from the starting of the
. . ~
freeze-drying operation until it is completed. This
relatively long time is a source of added cost to the
product and annoyance and irritation to the personnel.
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Accordingly, this invention provides a process
for preparing essentially crystalline cephalothin sodium for
reconstitution for parenteral administration by a freeze-
drying process requiring less than 24 hours compxising the
steps of: .
(a) dissolving from 20 to 40 percent (w/w) of
said cephalothin sodium in a solvenk com-
prised of from 2 to 10 percent of a Cl-C3
alcohol or acetone and from 98 to 90 percent
water (v/v);
(b) cooling the solution from (a) to -20C. or
below;
. (c) warming the preparation ~rom (b) to a tem-
: perature of between -3C. and -10C.;
(d) maintaining the temperature of the prep-
aration from (c) at from -3C. to -10C. for
a period of 3 hours or more;
(e) cooling the preparation from (d) to -20C.
or below;
(f) reducing the pressure of the environment in
: which the preparation from (e) is maintained
to a maximum of 1 mm of mercury absolute;
(g) raising the temperature of the environment in
which the preparation from (f) is maintained . ~:
to a maximum of 50C., avoiding the melting
. of such preparation; and
... .
(h) subliming the solvent from the preparation
from (g) until the resulting crystals of said
- cephalothin sodium have a moisture content of
: not more than 1.0 percent, and a Cl-C3 alcohol
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or acetone content of not more than 1.0
percent.
The useful process of the present invention
comprises a procedure utilizing a ~reez,e-drying operation
wherein from 20 to 40 percent (w/w) of cephalothin sodium is
dissolved in a solvent system comprised of from 2 to 10
percent Cl-C3 alcohol or acetone and from 98 to 90 percent
water. Such a solution is achieved by heating the solution
to a temperature of up to 70C. to effect complete solu-
bilization. The resulting solution can be sterilizecl by
filtration if desired. The solution is then exposed to an
environment in which the solution is cooled rapidly to a
temperature of -20C. or below, preferably -40C. The
cooling period may be completed in from 1 to 3 hours.
After the rapid cooling to -20C. or below,
preferably -40C., *he frozen solution is warmed to between
-3C. and -10C. and held at such temperature for 3 hours,
or more, to assure complete crystallization.
Once the frozen solution has been held at -3C.
to -10C. for 3 hours or more, it is again cooled to -20C.
or below, pre~erably -40C.
Following the critical steps just described, a
conventional freeze-drying operation is employed to sublime
the ice, leaving cephalothin sodium crystals having a
moisture content of not more than 1 percent and a Cl-C3
alcohol or acetone content of not more than 1 percent. Such
crystals have a suitable storage stability of three years or
more at room temperature, and dissolve in one minute or less
in an acceptable pharmaceutical diluent in concentrations
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appropriate for parenteral administration. The improvement
in the freeze-drying rate of the cephalothin sodium prepared
by the process described above over the conventionally
prepared cephalothin sodium crystals freeze-dried from an
aqueous solution results in from about a 15 to about a 50
percent reduction in the time required to complete the
freeze-drying cycle.
The crux of the instant invention is found in the
combination of the use of the (Cl-C3 alcohol or acetone)-water
solvent system and the establishment of a super-saturated
solution of cephalothin sodium contained in such a solvent
system, and the rapid cooling of the solukion to -20C. or
~elow, preferably -40C. The presence of the Cl-C3 alcohol
or acetone i~ the solvent system acta as an anti-solvent and
reduces the solubility of the cephalothin sodium. It was
discovered that the cephalothin sodium is substantially less
soluble in a (Cl-C3 alcohol or acetone)-water solvent than
in water alone. Consequently, by warming the frozen solution
to from 3C. to -10C. the nucleation and crystalli~ation
can be completed in 3 hours or sli~htly more as compared to
the 14 to 20 hours required whell no alcohol or acetone is
used.
The (Cl-C3 alcohol or acetone)-water solvent
employed in the useful methoa of this invention can contain
from 2 to 10 percent of a Cl-C3 alcohol or acetone and from
98 to 90 percent water (v/v). The preferred solvent system
is comprised of from 3 to 5 percent by volume of a Cl-C3
alcohol or acetone and 97 to 95 percent by volume of water.
In practice the cephalothin sodium is dissolved preferably -
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in the water and a volume of a Cl C3 alcohol or acetone,
preferably 95 percent ethanol, equal to 4 percent of the
volume of the solution of the cephalothin sodium, is added
to such solution.
The Cl-C3 alcohols which may be used include
methanol, ethanol, n-propanol and isopropanol. .
A concentration of cephalothin sodium of from
20 to 40 percent w/w in the Cl-C3 alcohol- or acetone-water
solvent is satisfactory for developing the large crystals on
freeze-drying. The preferred range is from 25 to 35 percent
w/w. Especially preferred is a 30 percent ~w/w) solution of
cephalothin sodium. In practice, one especially preferred
concentration of cephalothln sodium is provided by dis-
~olving 30 gm of cephalothin sodium in water ~. s'd. to
100 grams and adding thereto 3.55 ml of 95 percent grain
. alcohol, making a solution containing about 29 percent (w/w)
of the solute.
Sterilization of (Cl-C3 alcohol or acetone)-water
solution of cephalothin sodium can be achieved by filtering
20 such solution through sterile filtering means known to those :
skilled in the art and collecking the i}trate in a pre-
~` viously ~terilized container. Illustratively, sterile
filtering can be effected using a heat sterilized plate and
frame filter press equipped with an asbestos pad, or a
filtering membrane of cellulose acetate or nitrate, or a
candle having a porosity below 0.22 ~m.
.i The rapid cooling of the (Cl-C3 alcohol or acetone)-
water solution of cephalothin sodium can be best accomplished .
by exposing such solution to an environment of about -40C. -
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The temperature of the solution can be determined by locating
a thermocouple approximately in the center of the solution
to indicate the temperature at that point.
When the -20C., or lower, preferably -40C.
temperature has been reached following ~he method outlined
above, the frozen solution is warmed to from -3C. to -10C.
to initiate the nucleation and crystallization of the
cephalothin sodium. The frozen solution is held at a tem-
perature in that range for a period of 3 hours or more to
complete the crystallization.
After such period of holding at from -3C. to
-10C., the frozen solution is again chilled to -20C. or
below, preferably -40C., to complete solidification. No
apparent benefit was found in holding the Erozen mass at -~0C.
or below, preferably -40C. after solidification was complete.
At this point essentially all of the cephalothin sodium is
present in the frozen mass as free crystals. A conventional
reeze-drying operation is then utilized to sublime the
solvent from the frozen mass leaving a deposit of essen-
tially crystalline cephalothin sodium.
The frozen cephalothin sodium preparation wherein
the nucleation of the crystals is substantially comp].ete is
subjected to an environment where the pressure can be
reduced to a practical maximum of no more than l mm mercury
absolute. It is preferable to reduce the pressure much more
than to l mm mercury absolute. The best results are obtained
with an absolute pressure of between 0.05 mm and 0.2 mm.
This latter pressure range is ordinarily readily attainable
in both laboratory and commercial freeze-drying apparatus,
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the design, construction and operation of which are all wel~
known to those skilled in the art. After the pressure of
the environment described above has been reduced to an
operating level~ heat is introduced into such an environ-
ment. The temperature of the environment is raised to a
point where the maximum sublimation rate can be achieved
without melting the frozen mass. As a ~eneral rule, the
temperature and the pressure are inversely related; the more
effective the pressure reduction, the higher the temperature
which can be employed in the subliming operation. As a
common guide it can be said that a maximum environment
temperature of 50C. can be reached with a highly efEicent
vacuum system where the absolute pressure is maintained at
about 0.05 mm absolute ~50 ~m). In any event, the tem-
perature should b~ ra~sed slowly so as to avoid overload~ng
the pressure-reducing system which can produce an undesirable
melting of the frozen mass. Preferably, the temperature of
the environment in the subliming operation should be main-
tained between 10C. and ~0C. with the pressure held at or
below 0.2 mm absolute.
Subliming of the ice from the frozen mass is
continued until the moisture content of the cephalothin
sodium crystals is below 1 percent and the Cl-C3 alcohol or
acetone content is below 1 percent. Such a specification
assures physical stability of the resulting crystals.
Cephalothin sodium does not crystallize as a hydrate.
The cephalothin sodium prepared as detailed above
is essentially crystalline. For example, physical ana~yses
of cephalothin sodium indicated a crystallinity of between
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92 and 100 percent. In any event, a sufficient~y high
amount of crystallinity was obtained to impart storage
stability; i.e., an absence of a yellowing of the substance
and loss of microbiological potency for up to 3 years at
room temperature. When the process is operated to include
the sterile filtering of the ceph~lothin sodium solution and
the freeze-drying is done under aseptic conditions the
cephalothin sodium crystals can be sterile filled into
previously sterili~ed ampoules in appropriate quantities or
reconstitution for parenteral administration.
In another aspect of this invention the procedure
outlined and discussed in detail hereinbefore is augmented
by an additional step which comprises filling a measured
volume o~ the (C~-C3 alcohol or acetone)-water solution
a~ter suitable sterile iltration into a previously ster-
ilized ampoule, such measured volume containing the quantity
of cephalothin sodium which is desired in such ampoule after
the freeze-drying operation. The ampoules containing the
(Cl-C3 alcohol or acetone) water solution o~ cephalothin
sodium are then processed in the same manner as described
above~ The resulting reeze-dried cephalothin sodium
ampoule is ready ~or sterile stoppering and capping.
In practice it i~ preferred to sterile fill a
measured volume of sterile (Cl-C3 alcohol or acetone)-water
cephalothin sodium solution into a previously sterilized
ampoule as at least two beneficial results are obtained.
First, a more precise and consistent quantity of the
cephalothin sodium can be illed into an ampoule in the
liquid form than in the solid crystals form. And, second,
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it is much easier to achieve and maintai~ sterile operatingconditions in liquid filling operations than in dry filling
operations. Moreover, air pollution is less of a problem
when handling liquids than dry materials.
Alternatively, a quantity of sodium bicarbonate,
equal to from 2 to 5 percent, preferably 3 percent, of the
cephalothin sodium can be added to the cephalothin solution
before sterile filtration. Such an addition provides a
crystalline cephalothin sodium which after reconstitution
will have approximately a neutral p~, helping to reduce the
stinging experienced on I.M. administration.
The instant invention is further illustrated by
the following examples.
PROCEDURE I
Five hundred grams of cephalothin sodium having a
moisture content of 1 percent were dissolved in 1166.6 grams
of water for injection, U.S.P. ~ -
The resulting water solution of cephalothin sodium
was warmed to 62C. to complete solution and filtered through
a 0.45 ~m "Millipore"* membrane into an appropriate vessel.
The resulting aqueous solution containing 30
percent cephalothin sodium (w/w) was used in S0 ml. aliquots
in the following examples.
EXAMPLE I
Fifty milliliters of the 30 percent (w/w) cephalothin
sodium solution was combined with 2 ml. of 95% grain alcohol
(equivalent to 4% v/v).
*Trademark
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The ethanol-water solution of cephalothin sodium
was filled into previously sterilized vials in an amount of
3.56 ml. per vial. The quantity of solution was calculated
to provide 1 gram ampoules of cephalothin sodium.
The filled vials were placed in a con~entional
freeze-drying unit and the temperature of the solution was
lowered rapidly to -35C. over a period of less than 3 hours
and then the temperature was warmed to -7~C. as quickly as
possible. The vials were held for 3 hours plus after the
frozen mass had reached a temperature of about -7C.
Then the vials were cooled to -35C. after ~eing
held for a little more than 3 hours at -7C.
The pressure in the ~reeze-dryer was reduced to
below 0.2 mm mercury absolute and the temperature was raised
to 10C. for khe sublimation of the ethanol-water solvent.
Eventually the temperature was raised to 25C. taking care
not to melt the frozen mass in the vials. When the sub-
limation process was completed, the vacuum was released and
the resulting vials were tested for moisture content,
ethanol content and reconstitution time.
Typical moisture content on individual vials was
0.10 and 0.11 percent.
Two vials tested or ekhanol residue showed less
than 0.5 percent.
Five vials examined for reconstitution time required
between 30 and 60 seconds to dissolve the cephalothin sodium
in 4.0 ml. of water for injection, U.S.P.
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EXAMPLE II
Two milliliters of methanol ~ere added to 50 ml.
of the 30 percent ~w/w) cephalothin sodium solution from
Procedure I. (E~uivalent to 4% v/v).
The methanol-water solution of cephalothin sodium
was filled into previously sterilized vials in an amount of
3.56 ml. per vial. The quantity of solution was calculated
to provide 1 gram ampoules of cephalothin sodium.
The filled vials were placed in a conventional
freeze-drying unit arld the temperature of the solution was
lowered rapidly to -35C. over a period of less than 3 hours
and then the temperature was warmed to -7C. as quickly as
possible. The vials were held Eor 3 hours plus aEter the
frozen mass had reached a temperature of -7C.
Then thé vials were cooled to -35C. after being
held for a little more than 3 hours at -7C.
The pressure in the freeze-dryer was reduced to
below 0.2 mm mercury absolute and the temperature was raised
to 10C. for the sublimation of the methanol-water solvent.
Eventually the temperature was raised to 25C. taking care
not to melt the frozen mas~ in the vials. When the sub-
limation process was completed, the vacuum was released
and the resulting vials were tested for moisture content,
methanol content and reconstitution t1me.
Typical moisture content on individual vials
was ~.10 and 0.11 percent.
Two vials tested for methanol residue showed less
than 0.5 percent.
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Five vials examined for reconstitution time
required between 30 and 60 seconds to dissolve the cephalo-
thin sodium in 4.0 ml o~ water for injection, U.S.P.
EXAMPLE III
Acetone in a volume of 2.0 ml. was added to 50 ml.
of the 30 percent (w/w) cephalothin sodium solution from
Procedure I. (Equivalent to 4% v/v).
The acetone-water solution of cephalothin sodium
was filled into previously sterilized vials in an amount of
3.56 ml. per vial. The quantity o solution was calculated
to provide 1 gram ampoules of cephalothin sodium.
; The filled vials were placed in a conventional
freeze-drying unit and khe temperature of the solutlon was
lowered rapidly to -35C. over a period o~ less than 3 hours
and then the temperature was warmed to -7C. as quickly as
possible. The vials were held for 3 hours plus after the
frozen mass had reached a temperature of -7C.
Then the vials were cooled to -35C. after being
held for a little more than 3 hours at -7C.
The pressure in the freeze-dryer was reduced to
below 0.2 mm mercury absolute and the temperature was raised
to 10C. or the sublimation of the acetone-water solvent.
Eventually the temperature was raised to 25C. taking care
not to melt the frozen mass in the vials. When the sublimation
process was completed, the vacuum was released and the
resulting vials were tested for moisture content, acetone
content and reconstitution time.
Typical moisture content on individual vials was
0.10 and 0.11 percent.
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Two vials tested for acetone residue showed less
than 0.5 percent.
Five vials examined for reconstitution time
required between 30 and 60 seconds to dissolve the cephalo-
thin sodium in 4.0 ml of water for injection, W.S.P.
EXAMPLE IV
Two and one-half milliliters of isopropanol were
added to 50 ml. of the 30 percent ~w/w) cephalothin sodium
solution from Procedure I. (Equivalent to 5~ v/v).
The isopropanol-water solution of cephalothin
sodium was filled into previously sterilized vials in an
amount of 3.6 ml. per vial. The quantity of solution was
calculated to provide 1 gram ampoules of cephalothin sodium.
The filled vials were placed in a conventional
freeze-drying unit and the temperature o the solution was
lowered rapidly to -35C. over a period o~ less than 3 hours
and then the temperature was warmed to -7C. as quickly as
possible. The vilas were held for 3 hours plus after the
frozen mass had reached a temperature of -7C.
Then the vials were cooled to -35C. after being
held for a little more than 3 hours at -7C.
The pressure in the ~reeze-dryer was reduced to
below 0.2 mm mercury absolute and the temperature was raised
to 10C. for the sublimation of the isopropanol-water
solvent. Eventually the temperature was raised to 25C.
taking care not to melt the frozen mass in the vials. When ~ -
the sublimation process was completed, the vacuum was
released and the resulting vials were tested for moisture
content, isopropanol content and reconstitution time.
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Typical moisture content on individual vials was
0.10 and a. 11 percent.
Two vials tested for isopropanol residue showed
less than 0.5 percent.
Five vials examined for reconr,titution time
required between 30 and 60 seconds to dissolve the cephalo-
thin sodium in 4.0 ml of water for injection, U.S.P.
EXAMPLE V
A total of 10.657 grams of sodium bicarbonate were
dissolved in 954 grams of water for injection U.S.P. and
cooled to 5~C. Three hundred and seventy-five grams of
cephalothin sodium were added with stirring and the qolution
was hoated ~o 66.5C. to complete the dissolution of the
cephalothin sodium. The resulting solution wa8 filtered
through a 45 ~m membrane.
Eleven hundred milliliters of the filtrate were
collected and 44 ml. of 95~ grain alcohol added thereto.
The concentration of cephalothin sodium was 28 percent (w/w)
and the ethanol 4 percent (v/v).
The ethanol-water solution of cephalothin sodium
wa~ filled into previously sterilized vials in an amount of
3.75 ml. per vial. The quantity of solution was calculated
to provide 1 gram ampoules of cephalothin sodium.
The filled vials were placed in a conventional
freeze-drying unit and the temperature of the solution was
lowered rapidly to -35C. over a period of less than 3 hours
; and then the temperature was warmed to -7C. as quickly as
possible. The vials were held for 3 hours plus after the
frozen mass had reached a temperature of -7C.
X-4905 -17-
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Then the vials were cooled to -35C. after being
held for a little more than 3 hours at -7C.
The pressure in the ~reeze-dryer was reduced to
below 0.2 mm mercury a~solute and the temperature was raised
to about 10C. for the sublimation of the ethanol-water
solvent. Eventually the temperature was raised to 25C.
taking care not to melt the frozen mass in the vials. When
the sublimation process was completed, the vacuum was
released and the resulting vials were tested for moisture
content, ethanol content and reconstitution time.
Typical moisture content on individual vials was
0.10 and 0.11 percent.
Two vials tested for ethanol residue showed less
than O.S percent.
Five vials examined for reconstitution time
required between 30 and 60 seconds to dissolve the cephalo-
thin sodium in 4.5 ml. of water for injection, U.S.P.
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