CHITOSAN HYDROGEL AS A BASE FOR SEMISOLID DRUG FORMS

A transparent and water-soluble/miscible gel ointment base was obtained by dissolving 93% deacetylated chitosan F in a solution of lactic acid. Rheological tests indicated that such a base was stable when clotrimazole, piroxicam, estradiol, progesterone, lidocaine HCl or a sodium salt of heparin were used. On the other hand, liquefaction of the gels took place on dissolving metronidazole or suspending hydrocortisone. Gels prepared on the basis of 66% deacetylated chitosan B were less stable. Changes in their consistency depended on the drug introduced. Due to the formation of an adduct between the acetyloamide of chitosan B lactate and the OH-groups of metronidazole or hydrocortisone, the gel initially hardened but did subsequently liquefy. The lower stability of gels prepared using less extensively deacetylated chitosan and the possible interaction of chitosan of lower degree of deacetylation with drugs do not exclude the use of this biopolycation in the ex temporare preparation and application of semisolid drug forms.