Claims for Patent: 4,092,315

Summary for Patent: 4,092,315

Title:	Novel crystalline forms of prazosin hydrochloride
Abstract:	The invention relates to novel and valuable crystalline forms of the hypotensive agent prazosin hydrochloride. The anhydrous .alpha.-form is preferred because it is relatively non-hygroscopic and hence possesses important advantages in handling and formulation. The polyhydrate form of prazosin hydrochloride is preferred because of its low, uniform rate of dissolution.
Inventor(s):	Bianco; Ernest J. (Niantic, CT)
Assignee:	Pfizer Inc. (New York, NY)
Application Number:	05/662,937
Patent Claims:	1. The crystalline .alpha.-form of 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline hydrochloride characterized by the infrared spectrum in potassium bromide having the following absorption bands: 2. The process for preparing the crystalline .alpha.-form of 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline hydrochloride of claim 1 which comprises precipitation of said .alpha.-form after heating 2-[4-(2-furoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline hydrochloride, a hydrate or methanolate thereof, in the presence of an alkanol or cycloalkanol solvent having from about 5 to 7 carbon atoms at a temperature in the range of about 125.degree. to 160.degree. C., until formation of said crystalline .alpha.-form is substantially complete. 3. The process of claim 2 whrein said alcoholic solvent is isoamyl alcohol. 4. The process of claim 3 wherein said isoamyl alcohol is heated at a temperature of about 132.degree. C.