PROCESS FOR THE PURIFICATION OF PULQXETINE HYDROCHLORIDE
RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Application Nos.
60/726,502, filed October 12, 2005, 60/736,746, filed November 14,2005, 60/661,711, filed March 14,2005, and 60/773,593, filed February 14,2006
FIELD OF THE INVENTION
[0002] The present invention relates to a process for the purification of
duloxetine hydro chloride.
BACKGROUND OF THE INVENTION
[0003] Duloxetine HC1 is a dual reuptake inhibitor of the neurotransmitters
serotonin and norepinephrine. It is used for the treatment of stress urinary incontinence (SUl), depression, and pain management. It is commercially available as CYMBALTA®. Duloxetine hydrochloride has the chemical name (S)-(+)-N-methyl-3-(l-naphthalenyloxy)-3-(2-thienyl)propanamine hydrochloric acid salt and the following structure.
(Formula Removed)
[0004] Duloxetine, as well as processes for its preparation, is disclosed in a
few published documents, such as U.S. Patent No. 5,023,269, EP Patent No. 457559, and U.S. Patent No. 6,541,668.
[0005] The conversion of duloxetine to its hydrochloride salt is described in
U.S. Patent No. 5,491,243 and in Wheeler W.J., et at, J. Label.Cpds.Radiopharm, 1995, 36,312. In both cases the reactions are performed in ethyl acetate.
[0006] Like any synthetic compound, duloxetine HC1 can contain extraneous
compounds or impurities that can come from many sources. They can be unreacted
starting materials, by-products of the reaction, products of side reactions, or
degradation products. Impurities in duloxetine HC1 or any active pharmaceutical
ingredient (API) are undesirable, and, in extreme cases, might even be harmful to a
patient being treated with a dosage form of the API in which a sufficient amount of
impurities is present. Furthermore, the undesired enantiomeric impurities reduce the
level of the API available in the pharmaceutical composition.
[0007] It is also known in the art that impurities in an API may arise from
degradation of the API itself, which is related to the stability of the pure API during
storage, and the manufacturing process, including the chemical synthesis. Process
impurities include unreacted starting materials, chemical derivatives of impurities
contained in starting materials, synthetic by-products, and degradation products.
[0008] In addition to stability, which is a factor in the shelf life of the API, the
purity of the API produced in the commercial manufacturing process is clearly a
necessary condition for commercialization. Impurities introduced during commercial
manufacturing processes must be limited to very small amounts, and are preferably
substantially absent. For example, the ICH Q7A guidance for API manufacturers
requires that process impurities be maintained below set limits by specifying the
quality of raw materials, controlling process parameters, such as temperature,
pressure, time, and stoichiometric ratios, and including purification steps, such as
crystallization, distillation, and liquid-liquid extraction, in the manufacturing process.
[0009] The product mixture of a chemical reaction is rarely a single
compound with sufficient purity to comply with pharmaceutical standards. Side products and by-products of the reaction and adjunct reagents used in the reaction will, in most cases, also be present in the product mixture. At certain stages during processing of an API, such as duloxetine hydrochloride, it must be analyzed for purity, typically, by HPLC or TLC analysis, to determine if it is suitable for continued processing and, ultimately, for use in a pharmaceutical product. The API need not be absolutely pure, as absolute purity is a theoretical ideal that is typically unattainable. ' Rather, purity standards are set with the intention of ensuring that an API is as free of impurities as possible, and, thus, is as safe as possible for clinical use. In the United States, the Food and Drug Administration guidelines recommend that the amounts of some impurities be limited to less than 0.1 percent.
[00010] Generally, side products, by-products, and adjunct reagents
(collectively "impurities") are identified spectroscopically and/or with another
physical method, and then associated with a peak position, such as that in a
chromatogram or a spot on a TLC plate. (Strobel p. 953, Strobel, H.A.; Heineman,
W.R., Chemical Instrumentation: A Systematic Approach, 3rd dd. (Wiley & Sons:
New York 1989)).
[00011] (+)-N-methyl-3-(l-naphthalenyloxy)-3-(3-thienyl)propanamine is
disclosed by Olsen B.A et al, as an impurity obtained in the preparation of duloxetine
(J. Lib. Chrom. & Rel. Technol, 1996, 19,1993).
[00012] There is a need in the art for a process for preparing chemically and/or
enantiomerically pure duloxetine HC1
SUMMARY OF THE INVENTION
[00013] The present invention encompasses a process for the purification of
duloxetine HC1, comprising crystallizing duloxetine HC1 in water, or a solvent selected from the group consisting of C3-8 ketones, C3-8 esters, C2-8 ethers, C2-8 alcohols, and mixtures thereof with water.
DETAILED DESCRIPTION OF THE INVENTION
[00014] • As used herein the term "crystallizing" refers to a process comprising:
heating a mixture of a starting material and a solvent to a temperature of between
about 10°C below and above the reflux temperature of the solvent to obtain a solution,
and cooling the solution to a temperature of about 0°C to about 30°C.
[00015] The present invention encompasses a process for the purification of
duloxetine HC1, comprising crystallizing duloxetine HC1 in water, or a solvent selected from the group consisting of C3-8 ketones, C3-8 esters, C2-8 ethers, C2-8 alcohols, and mixtures thereof with water.
[00016] Preferably, the solvent is selected from the group consisting of acetone,
methyl ethyl ketone (MEK), ethyl acetate, methyl t-butyl ether (MTBE), ethanol, isopropanol, and n-butanol. Most preferably, the solvent is a mixture of acetone and water or isopropanol.
[00017] Preferably, when the solvent is in a mixture with water, the ratio
(vol/vol) of the solvent and water is at least about 97:3 to about 98.25:1.75.
Preferably, the ratio is at least about 98:2. Preferably, the ratio (vol/vol) of the
starting material and the water or solvent is about 1:10. Preferably, the dissolution
occurs at reflux temperature. Preferably, after cooling, the solution is maintained
while stirring, for about 10 minutes to about 24 hours.
[00018] Preferably, the duloxetine HC1 obtained after the crystallization is
purer than the duloxetine HC1 starting material. To exemplify, the obtained
duloxetine HC1 contains a lower level of the impurity (+)-W-methyl-3-(l -
naphthalenyloxy)-3-(3-thienyl)propanamine (DLX-ISO3) and a lower level of the
R-enantiomer of duloxetine.
[00019] The crystallization process may be repeated in order to increase the
purification even further either with the same or a different solvent that was used for
the first crystallization.
[00020] Having described the invention with reference to certain preferred
embodiments, other embodiments will become apparent to one skilled in the art from
consideration of the specification. The invention is further defined by reference to the
following examples, describing in detail the analysis of the duloxetine HC1 and
methods for preparing the duloxetine HC1 of the invention.
[00021 ] It will be apparent to those skilled in the art that many modifications,
both to materials and methods, may be practiced without departing from the scope of
the invention.
EXAMPLES
HPLC method for measuring chemical purity:
Column: Hypersyl Gold (150 x 4.6 5/i)
Mobile phase: (A) 63% (KH2PO4 (0.02M) pH-2.5): 37% (35%MeOH: 10%THF)
(B) 20% (KH2PO4 (0.02M) pH-2.5): 80% ACN
Gradient: From 0 to 15mm(A)isocraticaly
From 15 to 60 min (B) increases from 0 to 100%
Detection: 230 nm
Flow: 1 mL/min
Detection limit: 0.02%
HPLC method for measuring enantiomeric purity:
Column: Diacel Chiral OD 250 x 4.6 5ft
Eluent: Hexane (900mL):IPA (lOOmL): DEA(2mL)
Flow: 1 mL/min
Detection: 230 nm
Sample cone: 0.5mg/mL
Sample vol: lOOjuL
Column temp: 20°C Detection limit: 0.02%
Example 1: Purification of Duloxetine hvdrochloride in acetone/water Example la:
[00022] A mixture of 20 g Duloxetine hydrochloride in 204 ml acetone/water
(98:2) was heated to reflux. After the compound was dissolved, the oil bath was removed, and the solution was cooled to 15°C overnight. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (78 percent yield) containing DLX-ISO3 (0.21 percent) and enantiomer R (<0.03 percent)
Example 1b:
[00023] A mixture of 13 g of the previously obtained Duloxetine hydrochloride
in 130 ml acetone/water (98:1.5) was heated to reflux. After the compound was dissolved, the oil bath was removed, and the solution was cooled to 10°C for 2 hours. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (87 percent yield) containing DLX-ISO3 (0.15 percent) and free of enantiomer R.
Example 1c:
[00024] A mixture of 10 g of the previously obtained Duloxetine hydrochloride
in 100 ml acetone/water (98:2) was heated to reflux. After the compound was dissolved, the oil bath was removed, and the solution was cooled to room temperature and stirred for 1 hour. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (80 percent yield) containing DLX-IS 03 (0.07 percent), and free of enantiomer R.
Example Id:
[00025] A mixture of 7.5 g of the previously obtained Duloxetine
hydrochloride in 75 ml acetone/water (98:2) was heated to reflux. After the compound was dissolved, the oil bath was removed, and the solution was cooled to room temperature and stirred for 2 hours. The solid was filtered, washed with acetone, and dried in a vacuum oven at 40°C for 16 hours, giving Duloxetine
hydrochloride (73 percent yield) containing DLX-IS03 (0.03 percent), and free of enantiomer R.
Example 2: Purification of Duloxetine hydrochloride in acetone /water under different conditions Example 2a:
[00026] A mixture of 16 g Duloxetine hydrochloride (contaminated with 0.30
percent DLX-ISO3 and 0.13 percent enantiomer R) in 160 ml acetone was heated to reflux, and then 4 ml of water were added till complete dissolution. After the compound was dissolved, the oil bath was removed, and the solution was cooled to room temperature and stirred for one hour. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (68 percent yield) containing DLX-ISO3 (0.10 percent) and free of enantiomer R.
Example 2b:
[00027] A mixture of 8 g of the previously obtained Duloxetine hydrochloride
in 80 ml acetone was heated to reflux, and 2 ml of water were added. After the compound was dissolved, the oil bath was removed, and the solution was cooled to room temperature and stirred for half hour. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (36 percent yield) containing DLX-ISO3 (0.06 percent).
Example 2c;
[00028] A mixture of 2 g of the previously obtained Duloxetine hydrochloride
in 20 ml of acetone was heated to reflux, and 0.4 ml of water were added. After the compound was dissolved, the oil bath was removed, and the solution was cooled to room temperature and stirred for three hours. The solid was filtered, washed with acetone, and dried in a vacuum oven at 45 °C for 16 hours, giving Duloxetine hydrochloride (50 percent yield) free of DLX-IS 03.
Example 3: Purification of Duloxetine hydrochloride in ethyl acetate
[00029] A mixture of 2 g Duloxetine hydrochloride (contaminated with 0.46
percent DLX-IS03 and 0.13 percent enantiomer R) in 10 ml ethyl acetate was heated
to reflux, and 50 ml of ethyl acetate were added. The mixture was stirred at the same
temperature for 40 minutes, followed by cooling to room temperature and stirring for
two hours. The solid was filtered, washed with ethyl acetate, and dried in a vacuum
oven at 45°C for 16 hours, giving Duloxetine hydrochloride (93 percent yield)
containing DLX-ISO3 (0.28 percent) and 0.07 percent of enantiomer R.
[00030] Example 3 was repeated to yield Duloxetine hydrochloride containing
less than 0.14 percent DLX-ISO3.
Example 4: Purification of Duloxetine hydrochloride in IPA Example 4a:
[00031] A mixture of 8.4 g Duloxetine hydrochloride (contaminated with 0.29
percent DLX-ISO3 and 0.17 percent enantiomer R) in 84 ml IPA was heated to reflux. The solution was stirred at the same temperature for 15 minutes, followed by cooling to room temperature and stirring for two hours. The solid was filtered, washed with IPA, and dried in a vacuum oven at 45 °C for 16 hours, giving Duloxetine hydrochloride (62 percent yield) containing DLX-ISO3 (0.21 percent) and free of enantiomer R.
Example 4b:
[00032] A mixture of 8.8 g Duloxetine hydrochloride (contaminated with 0.21
percent DLX-ISO3) in 70 ml IPA was heated to reflux. The solution was stirred at the same temperature for 15 minutes, followed by cooling to room temperature and stirring for two hours. The solid was filtered, washed with IPA, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (83 percent yield) containing DLX-ISO3 (0.17 percent).
Example 4c
[00033] A mixture of 5 g Duloxetine hydrochloride (contaminated with 0.17
percent DLX-IS03) in 40 ml IPA was heated to reflux. The solution was stirred at the same temperature for 15 minutes, followed by cooling to room temperature and stirring for two hours. The solid was filtered, washed with IPA, and dried in a
vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (65 percent yield) containing DLX-ISO3 (0.13 percent)
Example 5: Purification of Duloxetine hydrochloride in MTBE /water: Example 5a
[00034] A mixture of 12 g Duloxetine hydrochloride (contaminated with 0.29
percent DLX-ISO3 and 0.11 percent enantiomer) in 120 ml MTBE was heated to reflux, and 3.6 ml of water were added until complete dissolution. The two phase solution was stirred at the same temperature for 15-30 minutes, followed by cooling to room temperature and stirring overnight. The solid was filtered, washed with the same solvents, and dried in a vacuum oven at 45 °C for 16 hours, giving Duloxetine hydrochloride (29 percent yield) containing DLX-ISO3 (0.16 percent) and less than 0.02 percent of enantiomer R.
Example5b:
[00035] A mixture of 2 g Duloxetine hydrochloride (contaminated with 0.16
percent DLX-ISO3 and less than 0.03 percent of enantiomer R) in 20 ml MTBE is heated to reflux, and 0.36 ml of water are added until complete dissolution. The two phase solution is stirred at the same temperature for 15 to 30 minutes, followed by cooling to room temperature and stirring overnight. The solid is filtered, washed with the same solvents, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (29 percent yield).
Example 6: Purification of Duloxetine hvdrochloride in MEK /water: Example 6a:
[00036] A mixture of 4 g Duloxetine hydrochloride (contaminated with 0.30
percent DLX-ISO3 and 0.17 percent enantiomer R) in 20 ml MEK was heated to reflux, and 0.6 ml of water were added until complete dissolution. The solution was stirred at the same temperature for 15-30 minutes, followed by cooling to 0° to 5°C and stirring for two hours. The solid was filtered, washed with the same solvents, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (32 percent yield) containing DLX-IS03 (0.10 percent) and free of enantiomer R.
Example 6b:
[00037] A mixture of 0.5 g Duloxetine hydrochloride (contaminated with 0.10
percent DLX-ISO3) in 2.5 ml MEK is heated to reflux, and 0,1 ml of water are added until complete dissolution. The solution is stirred at the same temperature for 15 to 30 minutes, followed by cooling to 0° to 5°C and stirring for two hours. The solid is filtered, washed with the same solvents, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (32 percent yield).
Example 7: Purification of Duloxetine hvdrochloride in water
[00038] A mixture of 2.7 g Duloxetine hydrochloride (contaminated with 0.50
percent DLX-ISO3 and 0.29 percent enantiomer R) in 27 ml water was heated to
reflux. The solution was stirred at the same temperature for 10 to 15 minutes,
followed by cooling to room temperature and stirring overnight. The solid was
filtered, washed with water, and dried in a vacuum oven at 45°C for 16 hours, giving
Duloxetine hydrochloride (61 percent yield) containing DLX-ISO3 (0.25 percent) and
free of enantiomer R.
[00039] Example 7 is repeated to yield Duloxetine hydrochloride containing
less than 0.14 percent DLX-ISO3.
Example 8: Purification of Duloxetine hvdrochloride in MEK
[00040] A mixture of 2 g Duloxetine hydrochloride (contaminated with 0.26
percent DLX-ISO3 and 0.17 percent enantiomer R) in 40 ml MEK was heated to . reflux. The solution was stirred at the same temperature for 30 minutes, followed by cooling to 0° to 5°C and stirring for 2 hours. The solid was filtered, washed with MEK, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (60 percent yield) contaminated with DLX-IS03 (0.21 percent) and free of enantiomer R.
[00041] Example 8 is repeated to yield Duloxetine hydrochloride containing
less than 0.14 percent DLX-ISO3.
Example 9: Purification of Duloxetine hvdrochloride in acetone
Example 9a:
[00042] A mixture of 2 g Duloxetine hydrochloride (contaminated with 0.46
percent DLX-ISO3 and 0.13 percent enantiomer R) in 130 ml acetone was heated to
reflux. The solution was stirred at the same temperature for one hour, followed by cooling to 27°C. The solid was filtered at the same temperature, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (59.50 percent yield) containing DLX-ISO3 (0.17 percent) and free of enantiomer R.
Example 9b:
[00043] A mixture of 1 g Duloxetine hydrochloride (contaminated with 0.17
percent DLX-ISO3) in 65 ml acetone was heated to reflux. The solution was stirred at the same temperature for one hour, followed by cooling to 27°C. The solid was filtered at the same temperature, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine hydrochloride (59.50 percent yield).
Example 10: Purification of Duloxetine hydrochloride in n-butanol
[00044] A mixture of 2 g Duloxetine hydrochloride (contaminated with 0.26
percent DLX-IS O3 and 0.17 percent enantiomer R) in 12 ml n-butanol was heated to
reflux. The solution was stirred at the same temperature for 10 minutes, followed by
cooling to room temperature and stirring for 1 hour. The solid was filtered, washed
with n-butanol., and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine
hydrochloride (75 percent yield) containing DLX-ISO3 (0.24 percent, prophetic data)
and 0.07 percent of enantiomer R.
[00045] Example 10 is repeated, using a solvent selected from: C3-5 ketones,
C3-5 esters, C2-5 ethers, C2-4 alcohols other than n-butanol and mixtures thereof with
water to yield Duloxetine hydrochloride containing less than 0.14 percent DLX-IS03.
Example 11: Purification of Duloxetine hydrochloride in ethanol
[00046] A mixture of 2.22 g Duloxetine hydrochloride (contaminated with 0.28
percent DLX-IS03 and 0.50 percent enantiomer R) in 22.2 ml ethanol was heated to
reflux. The solution w.as stirred at the same temperature for 15 minutes, followed by
cooling to room temperature and stirring for 1 hour. The solid was filtered, washed
with n-butanol, and dried in a vacuum oven at 45°C for 16 hours, giving Duloxetine
hydrochloride (36 percent yield) containing DLX-IS03 (0.21 percent) and free of
enantiomer R.
[00047] Example 11 is repeated to yield Duloxetine hydrochloride containing
less than 0.14 percent DLX-ISO3.
[00048] While it is apparent that the invention disclosed herein is well
calculated to fulfill the objects stated above, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art. Therefore, it is intended that the appended claims cover all such modifications and embodiments as falling within the true spirit and scope of the present invention.

What is claimed:
1. A process for the purification of duloxetine HCI, comprising crystallizing
duloxetine HCI in water, or a solvent selected from the group consisting of C3_
8 ketones, C3-8 esters, C2-8 ethers, C2-8 alcohols, and mixtures thereof with
water.
2. The process of claim 1, wherein the solvent is selected from the group
consisting of acetone, methyl ethyl ketone (MEK), ethyl acetate, methyl
t-butyl ether (MTBE), ethanol, isopropanol, and n-butanol.
3. The process of claim 1, wherein the solvent is a mixture of acetone and water
or isopropanol.
4. The process of any of claims 1 to 3, wherein the ratio (vol/vol) of the solvent
and water is at least about 97:3 to about 98.25:1.75.
5. The process of claim 4, wherein the ratio (vol/vol) of the solvent and water is
at least about 98:2.
6. The process of any of claims 1 to 3, wherein the ratio (vol/vol) of the starting
material and the water or solvent is about 1:10.
7. The process of any of claims 1 to 6, wherein the dissolution occurs at reflux
temperature.
8. The process of any of claims 1 to 7, wherein after cooling, the solution is
maintained while stirring, for about 10 minutes to about 24 hours.