Studies on the release of drugs from O/W emulsion ointments using the mathematical interpretations. Part 2: Influence of the ointment composition.

The empirical function Q = t/(A + Bt) has been applied to the quantitative description of the release process of salicylic acid from the emulsion ointment as influenced by its composition. The results as compared with those obtained by the use of Higuchi's "exponential" equation confirm the usefulness of the proposed equation, especially for thin ointment layers. It has been shown that there is a satisfactory correlation between the values of parameters 1/A, 1/B and thickness of the ointment layer and its composition. In this manner it is possible to predict the time course of the release process under other conditions.