Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE PURIFICATION OF NON-IONIC SOLVENTS FOR
STABILIZED INJECTABLE PHARMACEUTICAL FORMULATIONS
The present invention relates to a stabilized pharmaceutical composition in a
solvent system and in particular a co-solvent system suitable for preparing a
stabilized
injection composition containing at least one pharmaceutical agent. More
particularly, the
present invention relates to stabilized compositions of anti cancer drugs.
Administration of pharmaceutical compounds, particularly by injection,
usually requires a suitable solvent or delivery system to enable the
composition to be
administered to a patient.
An ideal solvent must typically have the following properties
1. It must be capable of solubilizing a therapeutically effective amount of
the active agent to produce an effective composition.
2. It must be compatible with the active agent.
It should be safe i.e. it should not cause any toxicity to the patient.
4. It should produce a composition having a good shelf life.
Many solvents while possessing most of the above advantageous qualities are
not particularly efficient in solubilizing the pharmaceutical agent to produce
an effective
composition for administration.
On the other hand numerous pharmaceutical agents are not sufficiently soluble
in any one solvent to enable the resulting composition to be effective.
Therefore, mixtures of
two or more solvents are quite commonly used in pharmaceutical industry to
overcome the
limitations of a single solvent to solubilize the active agent. These co-
solvent systems are
suitable for solubilizing many pharmaceutical agents, which cannot otherwise
be solubilized
or dispersed in a single solvent.
One example of a co-solvent system is a mixture of a polar solvent and a
non-ionic solvent, such as a mixture of a polyethylene glycol and Cremophor EL
or ELP
(polyethoxylated castor oil). Cremophor EL or ELP is a condensation product of
castor oil
and ethylene oxide sold by BASF.
Although these co-solvent systems can be effective in solubilizing many
compounds, they are not without their disadvantages. A commonly used co-
solvent system
used for many pharmaceutical agents is a 50:50 mixture of ethanol and
Cremophor ELP. A
potential problem associated with such solvents is that acids, salts or other
ionic impurities,
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as well as residual water in the solvent or solvent system, even if within the
acceptable limits,
can catalyze the degradation of the pharmaceutical agent. For example, co-
solvents of
ethanol and Cremophor are known to result in particulates forming upon
dilution with
infusion solutions. In addition, fibrous precipitates of unknown composition
form in some
formulations during storage for extended periods of time.
A solvent with sufficiently low levels of particularly deleterious impurities
will yield more stable pharmaceutical compositions. The US FDA approved
pharmaceutical composition of Taxol marketed by Bristol Myers Squibb is
paclitaxel in a
co-solvent of 50:50 by volume of dehydrated ethanol and commercial grade
Cremophor EL.
These compositions exhibit a loss of potency of greater than 60% after storage
for 12 weeks
at 500 C (US Patent 5,504,102). The loss of potency is attributed to the
decomposition of
paclitaxel during storage. It is believed that carboxylate anions present in
Cremophor EL can
catalyze the decomposition of paclitaxel, even at levels within the defined
limits set forth in
the National Formulary. U.S. Patent No. 5,504,102 (Agharkar et al)
incorporated herein by
reference discloses removing the carboxylate anions from polyethoxylated
castor oils
(cremophor) by acid addition or alumina adsorption. US Patent 5,504,102
discloses that
paclitaxel reacts with ethanol during storage and that the decomposition of
paclitaxel is
catalyzed by the carboxylate anions in the solvent. They also disclose that
lowering the
carboxylate concentration of the solvent produced a stabilizing effect on the
pharmaceutical
composition. The composition in question being Taxol, prepared as an injection
concentrate
containing 6 mg/ml paclitaxel in 50:50 by volume ethanol and polyoxyethylated
castor oil.
As per their disclosure, the pharmaceutical agents of interest are those
having
an ester linkage that can be cleaved by an alcohol in the presence of
carboxylate anions. In
their preferred embodiments, the solvent is a co-solvent mixture of at least
one solvent and a
solubilizing agent. The preferred solvent includes alcohol such as dehydrated
ethanol. The
solubilizing agent in preferred embodiments is a polyoxyethylated castor oil
such as that sold
under the tradename Cremophor EL or Cremophor ELP by BASF.
In their preferred embodiments, the carboxylate anion content of the solvent
is
lowered by a number of methods. In one embodiment of the invention, the
Cremophor EL or
other solvent is passed through a standard chromatography column of aluminum
oxide which
adsorbs the carboxylate anions as well as other impurities to reduce the
carboxylate anion
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content of the solvent. In an alternative embodiment, the solvent is treated
by the addition of
an acid in a stabilizing amount to reduce the carboxylate anion content to a
sufficiently low
level to substantially prevent catalyzed degradation of the pharmaceutical
compound.
Nikolayev et al in US Patent No. 5,925,776 disclose a method of reducing the
canon content in the polyethoxylated castor oil (crernophor). This is achieved
by pre-treating
the polyethoxylated castor oil with a strong cation exchange resin. The low
cationic content
polyethoxylated castor oil of the invention is then utilized to prepare
formulations of various
agents which are found to be sensitive to the previously commercially
available
polyethoxylated castor oil (cremophor EL). The stability of paclitaxel
formulated in a
mixture of low cationic content polyethoxylated castor oil of the invention
and ethyl alcohol
is shown to be better as compared to a formulation using untreated
polyethoxylated castor oil
of the invention and ethyl alcohol.
Anevski et al in US Patent No. 6,388,112 disclose a process for purifying a
non-ionic surfactant or solvent capable of dispersing and solubilizing a
pharmaceutical
compound. In the process, a solution of solvent and alcohol is brought in
contact with an
activated carbon column and an ion exchange resin column. The process is
particularly
adapted to the purification of polyethoxylated castor oils. The purified
solvent is useful in
the preparation of pharmaceutical compositions having enhanced shelf life,
such as for use
with paclitaxel.
Carver et al in US Patent No. 6,306,894 disclose a pharmaceutical
formulation of paclitaxel and polyethoxylated castor oil wherein the
formulation is relatively
acidified to a pH of less than 8.1 and preferably within a pH range of 5 to 7,
inclusively.
Ethanol is optionally included in the formulation. A formulation method is
also disclosed
and includes the step of mixing an acid with a carrier material, such as
polyethoxylated castor
oil, to form a carrier solution after which paclitaxel is added in an amount
such that the
resulting pH is less than 8. I and preferably in a pH range of 5 to 7. Ethanol
may optionally
be slurried with the paclitaxel before mixing with the carrier solution.
A variety of acidifying agents, a preferred one being anhydrous citric acid,
are
described. Acids in the form of powders, for example citric acid, have been
preferred over
those which contain water, for example sulfuric acid. The most preferred acid
for use in
accordance with the invention disclosed in US Patent 6,306,894 is citric acid,
but a wide
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range of acids may be used including
Citric acid-monohydrous, Citric acid-anhydrous, Citric acid-hydrous, Acetic
acid, Formic acid, Ascorbic acid, Aspartic acid, Benzene sulphonic acid,
Benzoic acid,
Hydrochloric acid, Sulphuric acid, Phosphoric acid, Nitric acid, Tartaric
acid, Diatrizoic acid,
Glutamic acid, Lactic acid, Malefic acid, and Succinic acid.
Owens et al in US Patent No. 6,071,952 disclose a pharmaceutical
composition with long term storage stability comprising a taxane or taxoid by
incorporating
an effective amount of an antioxidant.
Previous efforts to develop a shelf stable composition of some pharmaceutical
compositions in various co-solvent systems have not been entirely successful.
Thus, there is
a continuing need in the art for a solvent or co-solvent system capable of
being used for
preparing stabilized compositions and, in particular, stabilized injection
compositions
containing a pharmaceutical agent.
The disadvantages and limitations of the previous injection composition and
solvent systems are overcome by the present invention while providing a
convenient and
efficient method of producing a solvent and a method of stabilizing
pharmaceutical
compositions including compositions suitable for injection. The present
invention is
primarily directed to a solvent suitable for producing a stabilized
pharmaceutical composition
and to a method of producing and stabilizing a pharmaceutical composition.
The invention is directed to a solvent suitable for preparing stabilized
injection
compositions containing at least one pharmaceutical agent. Accordingly, it is
a primary
aspect of the invention to provide a method of preparing a treated solvent
which when used
in a composition has a stabilizing effect on the composition and a method of
preparing
stabilized pharmaceutical compositions using the treated solvent.
The stabilized pharmaceutical compositions produced using the treated
solvent of the invention have been shown to have a shelf life greater than the
compositions
produced from untreated solvent. The solvent system of the invention is
particularly suitable
for use with pharmaceutical compounds that exhibit decomposition, which is
catalyzed by the
presence of ionic, metallic and oxidizing impurities. The advantages of the
invention are also
attained by producing a stabilized pharmaceutical composition comprising at
least one
antineoplastic compound and a solvent system capable of solubilising the
antineoplastic
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compound, the solvent system comprising a solubilizing amount of an alcohol
such as
absolute alcohol and a solubilizer such as polyoxyethylated castor oil having
been purified to
have an impurities content sufficiently low to substantially minimize
degradation of the
antineoplastic compound.
Of particular interest are the antineoplastic agents such as paclitaxel,
teniposide, camptothecin and derivatives thereof.
DETAILED DESCRIPTION OF THE INVENTION
The solvent system of the invention essentially comprises a purified non-ionic
solvent The solubilizing agent can be a condensation product of an alkylene
oxide and a lipid
or fatty acid. The preferred solubilizing agent includes a polyoxyethylated
castor oil such as
that sold by M/s BASF under the tradename Cremophor EL or Cremophor ELP and an
alcohol. The polyoxyethylated castor oil is purified by a process of
chromatography to
reduce the water soluble ionic, metallic and oxidizing impurities to a
sufficiently low
concentration to minimize the decomposition of the pharmaceutical agent that
is catalyzed by
the presence of these impurities. The content of impurities in the
polyoxyethylated castor oil
is lowered by reverse-phase chromatography using suitable mobile and
stationary phases.
Further advantages of the invention are attained by providing a method of
stabilizing a pharmaceutical composition containing a pharmaceutical agent
such as
paclitaxel, teniposide, camptothecin and derivatives thereof, and a solvent
containing
absolute ethanol and a purified solubilizing agent as described above.
The invention provides a pharmaceutical stable formulation of paclitaxel made
using a purified solvent. The process involves purification of a non-ionic
solvent such as
polyethoxylated castor oil, preferably polyoxy-35-castor oil, more preferably
cremophor such
as Cremophor EL or Cremophor ELP using reverse-phase chromatography such that
the
content of ionic, metallic and oxidizing impurities of the cremophor is
lowered.
The process for purifying a non-ionic solvent comprising the steps of
(a) forming a solution of the non-ionic solvent in alcohol and water, with
or without the aid of heating;
(b) loading this solution on to a chromatography column packed with
reverse phase silica
(c) running the chromatograph using de-ionized water as the mobile
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phase to purify the solvent ;
(d) running the chromatograph using an eluent to recover the purified
solvent; and
(e) evaporating the residual water and the eluent.
Preferably the de-ionized water is HPLC grade.
The aqueous fractions obtained from rumiing the chromatograph using
de-ionized water are not used and may be set aside or discarded.
Preferably, the solvent is selected from polyethoxylated castor oil,
polyoxy-35-castor oil, Cremophor EL or Cremophor ELP.
Preferably, the alcohol is selected from methanol, ethanol, butanol,
iso-propanol etc; more preferably ethanol and more preferably dehydrated
ethanol.
The eluents may be selected from methanol, ethanol, isopropyl alcohol,
acetone, acetonitrile, tetrahydrofuran and other such solvents of similar
polarities. The
preferred eluent is acetone. Combinations of eluents may be used.
In one embodiment of the invention the mobile phase is run for 1 to 50
minutes; preferably for 20 minutes.
In one of the preferred embodiments of the invention, the polyethoxylated
castor oil is purified by loading it on a chromatography column packed with
reverse-phase
silica, preferably C-8 or C-18 and chromatographed using de-ionized water to
remove or
lower the concentration of water soluble impurities - both organic and
inorganic. The
purified polyethoxylated castor oil is then recovered by eluting the column
using an eluent,
preferably acetone. Preferably the de-ionized water is HPLC grade.
In a preferred embodiment the weight ratio of polyethoxylated castor oil to
alcohol is 10:1. In another embodiment of the invention the ratio of
polyethoxylated castor oil
to alcohol to water is 10 : 1 : 33 w/v/v.
The solvent purified by this method can be combined with antineoplastic
compound to form a composition. Optionally the compositions of this invention
include an
alcohol which may be added to the solvent before combining with the
antineoplastic agent,t
when the solvent is combined with the antineoplastic agent or after the
solvent is combined
with the antineoplastic agent. The alcohol may be a dehydrated alcohol.
Compositions
suitable for parenteral administration such as injection or infusion may be
prepared by
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diluting the compositions with a suitable parenteral fluid prior to parenteral
administration,
injection or infusion.
The following non-limiting example is intended to demonstrate the preferred
embodiment of the invention. One skilled in the art will readily recognize
that numerous
embodiments of the invention can be practiced to achieve the stabilizing
effect.
Example - 1
This example was carried out to demonstrate the effect of purification of
cremophor using reverse phase chromatography on the stability of Paclitaxel
formulation.
300 gm of Cremophor ELP (of M/s BASF) was diluted with about 30 ml of
absolute ethanol and the mixture was then dissolved in one litre of HPLC grade
de-ionized
water pre-heated to 60°C with stirring to make uniform solution.
This cremophor solution was then loaded on to a chromatography column ( 15
cm x 30 cm) packed with reverse-phase silica, preferably C-8 or C-18, having
an average
particle size of 30 to 60 p. The system was eluted using de-ionized HPLC grade
water as the
mobile phase for about 20 minutes to remove or reduce the water-soluble
impurities in the
cremophor. The eluted aqueous fractions were discarded. The column was then
eluted with
100% acetone to recover the purified cremophor. Acetone was completely removed
by
evaporation under vacuum using rotavapor at 40°C. The so obtained
cremophor was further
dried under vacuum at elevated temperature of about 55°C to remove the
residual water to
obtain purified cremophor.
The purified cremophor so obtained was tested for various impurities
including anions and canons. The canon and anion content was measured in the
cremophor
before and after purification and the results are as below
Cation Content
Identity Zinc Magnesium Sodium PotassiumAluminum Tin Calcium
Cremophor
ELP (BASF)2.93 7.86 28.67 3.00 0.78 1.28 32.62
ELP-Prep 2.10 5.99 31.39 3.36 0.33 0.78 22.25
1
ELP-Prep 1.89 4.60 31.52 3.48 0.37 0.32 17.83
2
ELP-Prep 1.58 4.60 32.12 3.39 0.13 0.33 18.89
3
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All values are in ppm
As is evident from the above table there is substantial decrease in the
concentrations of most of the cations listed above except sodium and
potassium. All the
above tabulated cations are known to promote degradation of paclitaxel.
Anion Content
Identity Chloride Bromide Sulphate
Cremophor
ELP (BASF) 23.211 0.657 6.747
ELP-Prep 1 4.625 ND 2.545
ELP-Prep 2 14.673 ND 6.014
ELP-Prep 3 15.386 ND 2.352
All values are in ppm; ND = Not detectable
As is evident from the above table there is a decrease in the concentrations
of
the inorganic anions, as compared to the untreated Cremophor ELP from M/s
BASF.
These purified cremophor samples were then used to make formulations of
paclitaxel and
subjected to stress temperature studies to see the effect on formation of
degradation products
of paclitaxel.
Samples 1 to 3 were prepared by dissolving 6 mg/ml of paclitaxel in 50 : 50
v/v mixture of purified cremophor ELP and absolute ethanol. The Cremophor ELP
of the
samples 1 to 3 was purified as discussed above. Sample 4 was prepared as a
control sample
from unprocessed Cremophor ELP in a 50 : 50 v/v mixture of unprocessed
Cremophor ELP
and ethanol with paclitaxel in the amount of 6 mg/ml.
The samples were then subjected to a stress temperature study at
50°C. The
results obtained are summarized as below
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Table -1
Paclitaxel
Degradation
Products
% at 50C
Total
(1:10 dilution (Inciudtng
in water) other
degradation
products)
3 10 30
Cremophor Formulation
Days Days Days
Sample 5.02 5.04 0.07 0.14 0.24
1
0 Sample 5.03 5.08 0.09 0.16 0.28
2
Sample 5.10 5.12 0.09 0.13 0.23
3
Sample 5.70 ~ 5.71 ~ 0.62 1.29 1.79
4 ~ ~ ~
The degradation products of paclitaxel include : Baccatin III, Ethyl Ester
Side
5 Chain of Paclitaxel , 10-Deacetyl Paclitaxel, 10- Deacetyl- 7- Epi-
paclitaxel, and 7
Epi-paclitaxel.
As is evident from the above results, purification of cremophor results in
reduction of the pH of cremophor from about 5.70 to around 5.10. As shown in
Table 1 -
Samples 1 to 3 prepared with purified cremophor are much,more stable in terms
of
degradation products of paclitaxel as compared to sample - 4. Thus, cremophor
ELP purified
using the process of the invention improves the stability of paclitaxel
formulation
significantly as compared to the formulation made using untreated Cremophor
BLP.
The foregoing description of the preferred embodiment of the invention has
been presented for purpose of illustration and description. It is not intended
to be exhaustive
or to limit the invention to precise parameters disclosed. Obvious
modifications or variations
are possible in light of the above teachings. The embodiment has been chosen
and described
to provide the best illustration of the principles of the invention and its
practical applications
to thereby enable one of the ordinary skill in the art to utilize the
invention in various
embodiments and with various modiftcations like using various size
chromatographic
columns, different types of reverse-phase chromatographic materials, column
packing
materials of different particle size, andlor different chromatographic
temperatures etc. All
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such modifications and variations are within the scope of the invention as
determined by the
appended claims.
