ABSTRACT
Objective: To optimize the composition of Compound Cheqinggao microemulsion and investigate its stability. Methods: Suitable emulsifier, co-emulsifier, and oil phase were selected by solubility method, and the pseudo ternary phase diagram was drawing by water titration. Then, the factors with the mass fraction of emulsifier, co-emulsifier, and oil phase as the independent variables, and the drug loading and particle size as response value, using Box-Behnken design-response surface method to determine the best prescription ratio and investigate its stability. Results: The optimal composition of substrate from Compound Cheqinggao microemulsion was as follows: 33% of polyoxyethylene hychogenated castor oil (RH40), 16% of polyethylene glycol (PGE400), 16% of Isopropyl palmitate, and 35% of water. Under these conditions, drug loading was 224.17 mg/mL and the particle size was 56.50 nm. Compound Cheqinggao microemulsion has good stability at 4 ℃ and 25 ℃ in dark conditions. Conclusion: The prepared microemulsion has good appearance, high drug loading, suitable particle size, and good stability, which could greatly increase the solubility of Compound Cheqinggao volatile oil.