Author/Editor     Kristl, A; Srčič, S; Vrečer, F; Šuštar, B; Vojnovic, D
Title     Polymorphism and pseudopolymorphism: influencing the dissoltion properties of the guanine derivative acycloric
Type     članek
Source     Int J Pharm
Vol. and No.     Letnik 139
Publication year     1996
Volume     str. 231-5
Language     eng
Abstract     In this work we established that acyclovir exists in hydrated form and that the ratio between acyclovir and water molecules in the crystal structure is 3:2. The anhydrous crystaline form of acyclovir was also prepared. Both crystalline forms were examined by means of thermal analyses, X-ray powder diffraction, infrared spectroscopy, solubility and dissolution rate studies. The differences in almost all tested parameters between the acyclovir hydrated and anhydrous forms were observed. They were explained by different crystal forms of the substances examined. It was found, that besides hydrate, two anhydrous forms of acyclovir are present: the unstable one, obtained at a drying temperature below 150 degree C (which converts to the hydrate almost immediately in the atmosphere), and the stable one, obtained at drying temperatures above 150 degree C (which shows, on heating to 172 degree C, the solid-solid transition). It was thus postulated that acyclovir can exist as a pseudopolymorphic and polymorphic solvate.
Descriptors     ACYCLOVIR
SOLUBILITY
SOLVENTS
POWDERS
CRYSTALLIZATION
WATER
X-RAY DIFFRACTION
SPECTROPHOTOMETRY, INFRARED