SOLUBILITY PHASE-DIAGRAM OF PRAZIQUANTEL ENANTIOMERIC SYSTEM

The solubility behaviour of praziquantel enantiomeric system at -15 de grees C, 4 degrees C, and 15 degrees C is presented. This system exhib its both a pseudoracemate behaviour and one which leads to the formati on of enantiomerically pure crystals. For solutions with lower enantio meric purity, the pseudoracemate behaviour is more prominent. Solid so lutions are formed when the mixtures of the enantiomers are crystallis ed. The phase diagram shows a complete absence of a eutectic. For mixt ures with higher enantiomeric purity, pure crystals of the excess enan tiomer are obtained when the solution is crystallised. Temperature dep endency of this polymorphism is not significant. With these phase diag rams, a method is suggested to obtain enantiomerically pure isomers of praziquantel from a partially resolved mixture. (C) 1995 Wiley-Liss, Inc.