The purpose of the present investigation was to develop and evaluate a self-microemulsifying drug delivery system (SMEDDS) for improving the oral absorption of a pranlukast hemihydrate (PLH), a very poorly water-soluble drug. An efficient self-microemulsifying vehicle for PLH was selected and optimized using solubility testing and phase diagram construction. The formulations were characterized by assessing self-emulsification performance, droplet size analysis, in vitro drug release characteristics and formulation stability studies. Optimized formulations for in vitro dissolution and bioavailability assessment were Triethylcitrate (TEC; 10%), Tween 20 (50%), Span 20 (25%), triethanolamine (5%), and benzyl alcohol (10%). The SMEDDS readily released the lipid phase to form a fine oil-in-water microemulsion with a narrow distribution size. Saturated solubilities of PLH from SMEDDS in water, pH 4.0 and 6.8, were over 150 times greater than that of plain PLH. The release of 100% PLH from SMEDDS was considerably greater compared to only 1.12% in simulated intestinal fluid (pH 6.8) from plain PLH after 2 hours. The PLH suspension with 0.5% sodium carboxymethylcellulose or 3% PLH-loaded SMEDDS was administrated at a dose of 40 mg/kg as PLH to fasted rats. The absorption of PLH from SMEDDS resulted in about a threefold increase in bioavailability compared with plain PLH aqueous suspension. Our studies illustrated that the potential use of the new SMEDDS can be used as a possible alternative to oral delivery of a poorly water-soluble drug such as PLH.
Keywords: PLH; SMEDDS; bioavailability; pranlukast hemihydrates; solubility.