Influence of formulation, receptor fluid, and occlusion, on in vitro drug release from topical dosage forms, using an automated flow-through diffusion cell.

An automated flow-through diffusion cell apparatus was used for comparing the release rates of a naphthoic acid derivative, CD 271, from different topical formulations. The influence of the following parameters on CD 271 release from the formulations was investigated: receptor fluid composition, occlusion, weight of tested formulation, and dosage form type. The amount of tested formulation was shown to have no significant effect on the apparent release constant and lag time for an anionic oil-in-water emulsion and an aqueous gel. Occlusion affected drug release from the different dosage forms. Thus, occlusion increased CD 271 pharmaceutical availability for a lotion and a hydroalcoholic gel containing 0.1% of solubilized drug. The release profile of CD 271 from the formulations was highly dependent on the receptor fluid composition. Drug release was dramatically enhanced with n-octanol as compared to an aqueous solution of surfactant. Using occlusive or nonocclusive procedures, CD 271 apparent release constant and lag time were found to be highly dependent on the type of tested formulation. The flow-through diffusion cell proposed in the present study allows an accurate comparison of drug release characteristics from prototype topical formulations and therefore represents a valuable tool for formulation research or quality control process.