Lipid-based formulations to enhance oral bioavailability of the poorly water-soluble drug anethol trithione: Effects of lipid composition and formulation

This study has explored the use of lipid-based formulations to enhance the oral bioavailability of the poorly water-soluble drug anethol trithione (ATT), and compared the performance of different formulations. Two groups of lipid-based formulations, sub-microemulsion (SME) and oil solution, were prepared using short (SCT), medium (MCT) and long (LCT) chain triglycerides respectively; aqueous suspension was used as the reference formulation. In vitro and in vivo studies were conducted to investigate the impact of lipid composition and formulation on drug absorption. In vitro digestion was used to analyze lipid digestion rates and drug distribution/solubilization. After in vitro digestion, the performance rank order for drug solubilization was SCT < MCT < LCT. SME formulations were digested more rapidly in vitro than oil solutions. The bioavailability of the drug from different formulations was investigated in rats. All six lipid-based formulations enhanced drug absorption compared to the aqueous suspension. For the SMEs, which were rapidly digested, in vivo bioavailability increased in accordance with the increase of solubilization data obtained by in vitro digestion, with the rank order SCT-SME < MCT-SME < LCT-SME. For the oil solutions, which were digested more slowly, there was no significant difference in drug bioavailability for the different formulations. In conclusion, lipid-based formulations can enhance the oral bioavailability of ATT, and for this BCS class II drug, both the lipid composition and type of lipid formulation are likely to govern in vivo performance.