Antioxidant assessment on promethazinr HCl decomposition using RP-HPLC assay method

The objective of this study was to investigate the effect of different sodium metabisulfite (SMBS) concentrations under a variety of ICH recommended test conditions. An attempt was made to test the feasibility of increasing shelf life when stored under different conditions. The promethazine hydrochloride (HCL) sample solutions used according to USP 24 and BP 1999 were prepared using different concentration of sodium metabisulfite as antioxidant. Standard solution was prepared using reference promethazine and analyses were done by employing reversed-phase high-performance liquid chromatography (RP-HPLC). The method used is efficient in acceptable resolution. The effect of different concentrations of SMBS on promethazine was investigated in promethazine HCL degradation. Chemical and physical stability was conducted in different conditions. The result shows that the drug was liable to degradation in basic pH medium condition, though the extent of degradation varied. Separation of the drug and the degradation products under various conditions was successfully achieved. The method was validated and the response was linear (r=0.9998) in the drug concentration range of 5 to 50 mu g. The mean values ( plus or minus RSD) of slope and intercept were 46376 ( plus or minus 0.006975) and 200049 ( plus or minus 0.4009), respectively. The recovery of the drug ranged between 98.3 and 101.16% from the mixture of degradation products. SMBS concentration influences the degradation process. Increase in concentration resulted in decrease of promethazine degradation. The developed method is simple and accurate in use for analysis of the drug and its degradation products. Antioxidant (SMBS) has important role in preventing promethazine degradation beside other factors.