Objective: To prepare bufotoxin microemulsion and investigate its physicochemical properties and in vitro penetration characteristics. Method: Bufotoxin microemulsion prescription was screened by solubility tests and pseudo-ternary phase diagrams;Morphology

particle size

Zeta potential and stability of microemulsion was investigated;In vitro transdermal process of bufotoxin microemulsion was investigated by transdermal diffusion instrument.The content of bufotoxin was determined by RP-HPLC

chromatographic conditions were as follows:ZORBAX SB-C18 column(4.6 mm×150 mm

5 μm)

mobile phase of methanol-water(70:30)

flow rate 1.0 mL·min-1

column temperature 30 ℃

detection wavelength 300 nm

injection volume 10 μL. Result: Optimal microemulsion formulation consists of GTCC-Cremophor RH 40-Transcutol HP-water(10.47%:33.69%:11.23%:44.61%)

drug loading of (1.36±0.12)%.Appearance of bufotoxin microemulsion was round

average particle size

PDI and Zeta potential were (31.33±5.362) nm

(0.103±0.025) and-(30.85±3.25) mV

respectively.Cumulative amount and skin retention amount of bufotoxin microemulsion in 12 h were 1 339.32 μg·cm-2 and 1 895.36 μg

which was 3.96 and 4.89 folds higher than that of bufotoxin saturated solution

respectively. Conclusion: Bufotoxin microemulsion was stable

it could significantly promote transdermal absorption of bufotoxin.