Swelling of and drug release from monoglyceride-based drug delivery systems.

Depending on the water content, unsaturated monoglycerides form various liquid crystalline phases, which can be used as sustained-release carriers. The aim of this study was to investigate the water uptake of and drug release from melt-congealed monoglyceride-based drug carriers. The water uptake of the unsaturated monoglycerides monoolein and monolinolein followed second-order swelling kinetics and levelled off at about 50% water content, at which a highly viscous cubic phase was formed. The rapid formation of the cubic phase suggested that the drug release occurred mainly from this phase. The drug release followed the square-root of time relationship during the initial release phase. Chlorpheniramine maleate, an amphiphilic drug was not completely released because of binding to the cubic phase. The rate of water uptake increased and the maximum water uptake decreased with increasing temperature. The drug release could be controlled by varying the surface-to-volume ratio, the drug loading, and the water content of the lipid matrix. It was independent of the source of monoolein.