Optimization of a floating osmotic pump system of dipyridamole using central composite design-response surface methodology

A new type of floating osmotic pump of dipyridamole was designed in this paper.  Apparatus three (Chinese Pharmacopeia 2005, appendix XD) was employed for in vitro dissolution test in order to evaluate the release and floating behavior in a same experiment.  The system was optimized using central composite design-response surface methodology; where similarity factor (f₂) between the dissolution profile of prepared formulation and the target dissolution profile was taken as dependent factor, usage amount of polyoxyethylene (X₁, mg), NaCl (X₂, mg) and pore former (PEG4000, X₃, %) were taken as independent factors.  The optimization model was    (R = 0.996).  It was found that the dissolution profile could match the target dissolution profile under the condition of weight gain 8% – 9%, X₁ (20 – 34), X₂ (30 – 57), X₃ = 50.  It is also found that the minimum usage percentage of pore former is 35.1%.  The prediction results of the optimization model were good in the experiments.