Drug Release from Thermosetting Fatty Vehicles Filled into Hard Gelatin Capsules

Abstract

An initial in vitro study has been conducted to evaluate liquid filled hard gelatin capsules as potential sustained release products. Using the model compounds salicylic acid (a weak acid) and tioconazole (a weak base), release characteristics from a series of thermosetting fatty vehicles (Gelucires) have been investigated. Rapid and sustained release profiles were obtained by using different vehicles. Drug release obeyed the pH-partition theory, and a general relationship between the release rate of salicylic acid and vehicle HLB was found. However, a similar relationship could not be identified for the release of tioconazole. Drug release occurred by diffusion or erosion and diffusion processes, dependent on the vehicle employed. Diffusion release occurred relatively slowly (particularly with tioconazole) therefore for the model systems an erodible carrier would be required to achieve release rates consistent with dosing oral sustained release products.