[Studies on suspension ointments. Part 2: The Diffusion of salicylic acid as influenced by the colloid chemical properties of the vehicle (author's transl)].

A comparative study of the solubility and the diffusion of salicylic acid in two hydrocarbon gels (Plastibase, vaseline) has been made. It was found that there was no difference in solubility, whereas the diffusion rate was greater in Plastibase. The solubilities and the diffusion rates were identical in the liquid components of the gels. The difference in diffusion rate between the two gels is attributable to the different properties of the solids in the gels. The greater in vitro diffusion rate in Plastibase results in a more rapid drug release in vivo. Suspension ointments may be regarded as saturated solutions with an excess of the drug in suspension. For this reason, the studies were undertaken mainly on saturated solutions.