The impact of drug-loading factors on the solid-state form of ritonavir-mesoporous silica systems

Abstract

Among the formulation techniques used to enhance thesolubility and dissolution rate of poorly, aqueous-soluble drugs, mesoporoussilica drug delivery systems have shown promise. A range of processes areemployed to load drugs onto silica and solvent-based approaches are widelyemployed. This study aims to understand the influence of drug concentration insolvent and drug-silica ratio on drug solid-state form and amorphization withinsilica. Ritonavirwhich belongs to  BCS Class II was used asa model drug. Ritonavir wasloaded into Syloid®244FP using a solvent evaporationmethod. Ritonavir loading percentage was calculated based on the assumptionthat the entire specific surface area of silica is exposed and available fordrug adsorption.  Ethanolsolutions with 3 different ritonavir concentrations; 70%, 32% and 20% saturatedsolubility at 25°C were employed. Ritonavir was loaded into silica at 1:1, 1:2and 1:3 ritonavir:silica ratios.  Allsystems included ritonavir loaded beyond monolayer surface coverage. Ritonavir- Syloid®244 FP formulations were characterisedusing DSC, PXRD, FT-IR, and TGA. The results showed that all ritonavir-Syloid®244 FP systemsprepared contained ritonavir in a non-crystalline state.