Development of self-microemulsifying drug delivery systems for oral bioavailability enhancement of alpha-Asarone in beagle dogs.

A self-microemulsifying drug delivery system (SMEDDS) for enhancement of oral absorption of a poor water-soluble drug, alpha-Asarone (ARE), is reported. Solubility of ARE was determined in various vehicles. SMEDDS consisted of a mixture of oils, surfactants, and cosurfactants that were emulsified in an aqueous medium under the gentle agitation and digestive motility. Pseudo-ternary phase diagrams were used to identify the efficient self-emulsification regions. The particle size distribution of the resulting microemulsions was determined using a laser scatter particle size analyzer (LSPSA). The optimized SMEDDS formulations containing Ethyl oleate (20%), Tween 80 (60%), and PEG 400 (20%) were tested for in vitro dissolution. The percentage of ARE released from the SMEDDS was significantly higher than that from the conventional tablets. Oral bioavailability of ARE in the SMEDDS via the hard capsules and the conventional tablets was evaluated in fasted beagle dogs. The bioavailability of ARE formulated in SMEDDS showed approximately 4.8-fold higher bioavailability than that in the conventional tablets. The results indicated that SMEDDS is potentially a good drug delivery system for oral delivery of the hydrophobic compound ARE.