[Factors influencing liberation of drug from semisolid dosage forms].

Liberation of salicylic acid--as a model active agent--was investigated from white petrolatum, creams w/o and o/w types and hydrogels. Active agent was applied in suspended, dissolved forms, in inclusion complexes and solubilized state. The process of liberation was studied by a continuous through-flow method, with Hanson vertical diffusion cell. The results of experiments were evaluated by factorial design method. Increase of the concentration of salicylic acid, polarity of vehicle and solubilized state of drug increased the drug release. It was established that the partitioning released drug was the most important step of drug release. Factors changing partitioning influenced the liberation to the highest degree.