| abstract |
There is disclosed a method of converting gabapenting hydrochloride substantially free of inorganic salts to gabapenting form II. The method comprises the steps of: (1) obtaining gabapentin hydrochloride that is substantially free of inorganic salts; (2) mixing a solution of the gabapenting hydrochloride with an additional amine in a first solvent so as to obtain a precipitate comprising gabapenting; and then (3) recovering gabapentin form II from the precipitate. The precipitated gabapentin is a novel polymorphic form of gabapentin possessing a crystalline structure characterized by novel sets of peaks in the powder X-ray diffraction pattern and in the FTIR spectra. This newly disclosed polymorph of gabapentin is characterized herein as gabapentin form III. The recovery step may comprise, for example, one of two alternative methods, slurrying the gabapentin form II in methanol, and then filtering the suspension to obtain gabapentin form II, or solubilizing the gabapentin form III in methanol with heating by reflux, and then cooling the solution to obtain gabapentin form II by crystallization. |