OBJECTIVETo prepare paeonol microemulsion and microemulsion gel, and investigate its content, physical and chemical properties. Their transdermal properties in vitro were studied as well.

METHODIPM acted as oil phase, lecithin/APG as surfactant, 1,2-propanediol as cosurfactant, water was added dropwise to the oil phase to prepare paeonol microemulsion at room temperature using magnetic stirring. HPLC method were used to determine the content of paeonol in paeonol microemulsion. Transmission electron microscopy and laser particle size analyzer were used to determine the shape and size of the microemulsion. Carbopol 940 was uesd as substrate to prepare paeonol microemulsion gel. Franz diffusion cell was used for characterizing the microemulsion and gel transdermal properties in vitro.

RESULTThe paeonol microemulsion was O/W microemulsion. Its uniform particle size was 32 nm and was with roundness appearance and stable content. The steady-state permeation rates of paeonol saturated aqueous solution, microemulsion, and microemulsion gel were 47.846, 103.760, 70.401 microg x cm(-2) x h(-1), and their 12 h cumulative amount of infiltration were 657.179, 1 266.484, 881.217 microg x cm(-2), respectively.

CONCLUSIONThe 12 h cumulative infiltration and infiltration rate of paeonol microemulsion and microemulsion gel are better than the saturated aqueous solution. Paeonol microemulsion gel is a new dosage form for transdermal drug delivery.