Stability of captopril in invert sugar solution

Objective: To assess the stability of captopril in different concentrations of invert sugar solution and to verify the hypothesis that the antioxidant effect of invert sugar can inhibit captopril's oxidative degradation. Method: Captopril 1 mg/ml formulations were prepared in 0% (Milli-Q water), 1%, 10%, 30% and 85% w/v of invert sugar and stored at 5 °C. The formulations were sampled at intervals up to 30 days for assay of captopril using a stability-indicating high-performance liquid chromatographic method. Results: Captopril in formulations containing low concentrations (1%, 10%, 30% w/v) of invert sugar was significantly less stable than in the control formulation (captopril 1 mg/ml in Milli-Q water). In contrast, captopril in a formulation containing 85% w/v invert sugar was substantially more stable than in the control. Conclusion: Captopril formulated in a solution of 85% w/v invert sugar is stable for at least 2 weeks when stored at 5 °C.