Avtor/Urednik		Kristl, A; Srčič, S; Vrečer, F; Šuštar, B; Vojnovic, D
Naslov		Polymorphism and pseudopolymorphism: influencing the dissoltion properties of the guanine derivative acycloric
Tip		članek
Vir		Int J Pharm
Vol. in št.		Letnik 139
Leto izdaje		1996
Obseg		str. 231-5
Jezik		eng
Abstrakt		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.
Deskriptorji		ACYCLOVIR SOLUBILITY SOLVENTS POWDERS CRYSTALLIZATION WATER X-RAY DIFFRACTION SPECTROPHOTOMETRY, INFRARED