Objective: To screen the optimal formula for artemether oral microemulsion-in situ gel and evaluate its properties. Method: With liquidity and gelation capacity as indexes

the water phase was determined.The composition was screened by solubility assay

compatibility test

stability and adhesiveness of microemulsion-in situ gel system.Pseudoternary phase diagram was used to optimize the formula.The morphology

particle size

Zeta potential

viscosity

stability

gelation and gastric retention time in vivo of artemether microemulsion-in situ gel were investigated

respectively. Result: The optimal formula was as follows:artemether:glyceryl triacetate:cremophor EL35:transcutol HP:(0.3% gellan gum-0.1% sodium alginate with low viscosity)=0.5:4.5:5:5:85

the concentration of artemether in the microemulsion-in situ gel about 5 g · L-1. Artemether microemulsion-in situ gel in transmission electron microscope consisted of small spherical droplets

mean particle size

polydispersity index (PDI)

Zeta potential

viscosity of the drug delivery system were 20.90 nm

0.172

-19.5 mV and 15.32 mPa · s

respectively.After oral administration

it gelled in the stomach of rats immediately;six hours later

gel could still be observed and artemether could be detected in the stomach. Conclusion: The solubitily of artemether is significantly increased in microemulsion-in situ gel.The artemether microemulsion-in situ gel has characteristics of good gelation in stomach and suitable viscosity

it not only can prolong the gastric retention time of artemether but also is suitable for oral administration.