Patent ID: 7635717

Claim:
An acetone-free process for the preparation of Gabapentin of the following formula which consists essentially of: (i) preparing an ethanol-free aqueous solution of Gabapentin hydrochloride in water in a ratio of one part by weight of the Gabapentin hydrochloride to 0.5 to 3 parts by weight of the water; (ii) preparing an aqueous solution of an alkali metal base in a concentration in the range of 40-50% w/w; (iii) adding 0.08 to 0.3 parts by weight of the solution obtained in step (ii) to 1.5 to 4 parts by weight of the solution obtained in step (i) at a temperature in the range of 0 to 20 degree C. to form a resulting solution; (iv) heating the resulting solution gradually to a temperature in the range of 60-90 degree C.; (v) gradually cooling the resulting solution to a temperature in the range of 0 to 15 degree C. to obtain a precipitate; (vi) aging the precipitate for a period of time in the range of 0.5 hrs to 8 hrs at a temperature in the range of 0 to 15 degree C.; (vii) separating the precipitate from its mother liquor; and (viii) recrystallizing the precipitate from a mixture of isopropyl alcohol, methanol and water in a ratio ranging from 4.54-19.64:3.88-15.64:1 (v/v), wherein the ratio of isopropyl alcohol to methanol is in the range from 0.58:1 to 1.32:1 (v/v), to get Gabapentin of over 99.5% purity and another mother liquor, wherein Gabapentin has a chloride content of 100 ppm or less.