Optimization and in situ intestinal absorption of self-microemulsifying drug delivery system of oridonin

The objective of this study was to optimize and characterize an oridonin self-microemulsifying drug delivery system (SMEDDS) formulation. A central composite design (CCD) was used to investigate the influence of factors (oil percentage and surfactant to co-surfactant ratio (Sur/Co-s ratio)) on the responses including droplet size, polydispersity, equilibrium solubility and in situ intestine absorption rate. Furthermore, the desirability function approach was applied to obtain the best compromise among the multiple responses. It was found that oil percentage played a significant role on the droplet size and polydispersity. The drug equilibrium solubility was mainly contributed to oil percentage and less to Sur/Co-s ratio. The in situ intestinal absorption was influenced by both of the two factors, whereas the oil percentage played a more important role in absorption. The practical response values under the optimized formulation were in good accordance with the predicted values. Our results demonstrate CCD is of value in optimizing the SMEDDS formulation and understanding the effects of formulation compositions on SMEDDS properties.