Abstract
To examine the influence of drugs on the physicochemical stability of semisynthetic fatty suppositories, model suppositories containing various kinds of drugs were prepared with Witepsol H-15 and storage experiments were performed. It was shown that the stability of pharmaceutical properties was largely dependent on the solubility of drugs in the fatty vehicle (So). That is, the rate of polymorphic transition of the vehicle measured by X-ray diffraction was accelerated by lipid-soluble drugs but was not much affected by lipid-insoluble drugs. The melting points measured by DTA generally decreased with inrreasing So, but they all increased by about 2 or 3°C during storage. The softening time decreased with increasing So. The release properties measured at 37°C were dependent on the solubility of the drugs in the dissolution fluid (Sw) initially but became dependent on So during storage. This phenomenon is discussed on the basis of the transportion mechanism of drugs in the lipid phase.
