Objective:To improve the dissolution character in vitro of slightly soluble bergenin by using solid dispersion technology

and investigate the effect of the formulation of core tablets and coating on bergenin solid dispersion osmotic pump tablets release in vitro and optimize the formulation.Method:The bergenin solid dispersion was prepared by fusion method

and the phase solubility and dissolution test was also determined.The release in vitro was studied through cumulative release measuring.And the optimal formulation of bergenin solid dispersion osmotic pump tablets was selected via the single-factor method and orthogonal design.Result: The amount of plasticizer was found to have effect on release in vitro of bergenin solid dispersion osmotic pump tablets.The tablets with optimized formulation could achieve the desired one-order release profile during 12 hours and the cumulative release over 90 percent.Conclusion:The release behavior of the monolithic osmotic pump tablets based on the intermediat of bergenin solid dispersion followed one-order kinetics equation.