Influence of the composition of glycerides on the solid-state behaviour and the dissolution profiles of solid lipid extrudates.

A monoacid triglyceride and a partial glyceride were extruded below their melting ranges alone and together in different mixture ratios to investigate the influence of the chemical composition of the lipid matrix on the solid-state properties and dissolution characteristics. The partial glyceride exhibits a faster release of the drug compared to the triglyceride due to its surfactant properties. The lipid mixtures show rather complex solid-state behaviour and hence unexpected dissolution characteristics. Adding 10% (w/w) partial glyceride to a triglyceride matrix led to increased incidence of the unstable alpha-form of the triglyceride leading to recrystallization of the stable beta-form over time which causes fractal structures on the extrudate surface which decrease the dissolution rate. Adding 50% (w/w) partial glyceride to the triglyceride matrix also results in tristearin alpha-formation subsequently followed by recrystallization to the beta-form. But as 50% of the matrix consists of the partial glyceride the dissolution rate was faster than the rate obtained by pure triglyceride or the 9+1 (w/w) mixture of triglyceride and partial glyceride. The results of this study help in understanding the complex solid-state behaviour of solid lipid extrudates with different composition and to manufacture suitable lipid-based oral dosage forms.