delta crystalline form, stable, anhydrous of hydrochloride of prazosin and new process to prepare the delta crystalline form.

摘要

Anhydrous, stable, crystalline delta -form of prazosin hydrochloride, having an infrared spectrum in potassium bromide of FIG. 1 having the following sharp absorption bands at 7.95 mu , 13.3 mu , and a triplet at 9.95 mu and the x-ray diffractogram of FIG. 2 having sharp bands in 10.5 DEG , 12.0 DEG , 16.9 DEG , and doublets in 24.5 DEG and 26.5 DEG . The delta -form of prazosin hydrochloride is prepared by removing the water of crystallization of prazosin hydrochloride hydrate by azeotropic distillation with selected organic solvents having a boiling point in the range of 55 DEG -160 DEG C. The delta -form of prazosin hydrochlorie is useful as a hypotensive agent.