Objective: To optimize formulation of Ginkgo Folium bi-layer osmotic pump controlled-release tablets. Method: With accumulative release rate of total flavonol glycosides as index

single-factor tests were adopted to screen formulations of drug-layer

push-layer and coating solution

drug release behavior was evaluated by similarity factor method.Taking the amount of PEG4000 in coating solution

coating weight and the amount of polyoxyethylene in push-layer as independent variables

linearity of release curve and accumulative drug release in 16 h as dependent variables

central composite design-response surface methodology was applied to optimize formulation. Result: Optimum formula was as follows:polyoxyethylene amount of 120 mg

the amount of PEG4000 of 1.5 g

coating weight of 11%;accumulative release of total flavonol glycosides in 16 h was above 90%. Conclusion: Release curve of this preparation meets requirements with correlation coefficient of 0.996 4.This optimized formulation is stable and suitable for industrial production of Ginkgo Folium bi-layer osmotic pump controlled-release tablets.