Abstract
Simple and sensitive kinetic and spectrophotometric methods have been developed and validated for the determination of two hypoglycemic drugs, pioglitazone hydrochloride and glimepiride in bulk powder and in their pharmaceutical formulations. Both methods are based on the oxidative coupling of each drug with 3-methylbenzothiazolinone hydrazone / cerric sulphate system. The formation of the colored products was monitored spectrophotometrically by measuring the absorbance at 645 tun. Factors affecting the reactions were studied and optimized. The stoichiometries of the reactions were determined using the limiting logarithmic method and the proposed reactions pathways were postulated. The fixed time (at 20 min) method was utilized for constructing the calibration graph of pioglitazone hydrochloride at room temperature. Concentrations of the drugs were calculated using the calibration equation for fixed time method for pioglitazone hydrochloride and using direct absorbance measurement of reaction product for glimepiride where good correlations were obtained in the range 2 - 16 mu g ml(-1) of both drugs with limits of detection of 0.37 and 0.06 mu g ml(-1) for pioglitazone hydrochloride and glimepiride respectively.
No interference was observed from the excipients that are commonly present in the pharmaceutical formulations. The proposed methods were successfully applied to the determination of pioglitazone hydrochloride and glimepiride in their pharmaceutical formulations. The label claim percentages were 99.9 - 100.1 +/- 0.87 - 0.89 and 99.2 - 99.4 +/- 0.75 - 1.02 for pioglitazone hydrochloride and glimepiride respectively. Statistical comparison of the results with those obtained by reference spectrophotometric methods showed excellent agreement between the accuracy and precision of the two methods. The proposed methods have great value in their applications to the analysis of pioglitazone hydrochloride and glimepiride in quality control laboratories.