Self-microemulsifying drug delivery system (SMEDDS) of vinpocetine: formulation development and in vivo assessment

A new self-microemulsifying drug delivery system (SMEDDS) has been developed to increase the solubility, dissolution rate and oral bioavailability of vinpocetine (VIP), a poor water-soluble drug. The formulations of VIP-SMEDDS were optimized by solubility assay, compatibility tests, and pseudo-ternary phase diagrams analysis. The optimal ratio in the formulation of SMEDDS was found to be Labrafac : oleic acid : Cremophor EL : Transcutol P=40 : 10 : 40 : 10 (w/w). The average particle diameter of VIP was less than 50 nm. In vitro dissolution study indicated that the dialysis method in reverse was better than the ultrafiltration method and the dialysis method in simulating the drug in vivo environment. Comparing with VIP crude drug power and commercial tablets, (-)VIP-SMEDDS caused a 3.4- and 2.9-fold increase in the percent of accumulated dissolution at 3 h. Further study on the absorption property of VIP-SMEDDS employing in situ intestine of rats demonstrated that VIP in SMEDDS could be well-absorbed in general intestinal tract without specific absorption sites. In addition, the developed SMEDDS formulations significantly improved the oral bioavailability of VIP in rats. Relative bioavailability of (-)VIP-SMEDDS and (+)VIP-SMEDDS increased by 1.85- and 1.91-fold, respectively, in relative of VIP crude powder suspension. The mechanisms of enhanced bioavailability of VIP might contribute to the improved release, enhanced lymphatic transport, and increased intestinal permeability of the drug.