DEVELOPMENT AND VALIDATION OF A STABILITY-INDICATING ASSAY (RP-HPLC) METHOD FOR QUANTITATIVE ANALYSIS OF OXYBUTYNIN IN BULK DRUG AND EXTENDED RELEASE FORMULATION

*Mitesh D Phale and Dr. Shailesh Sharma

ABSTRACT

A novel stability-indicating reversed-phase (RP) HPLC method has been developed and validated for quantitative analysis of oxybutynin in the bulk drug and formulation. Use of a 250 mm × 4.6 mm, 5-μm particle size, C18 column with 40:60 (v/v) 0.1M phosphate buffer: acetonitrile (pH adjusted to 4.5 with orthophosphoric acid) as isocratic mobile phase enabled separation of the drug from its degradation products. The flow rate and detection wavelength were 1 ml/min and 203 nm respectively. The method was validated for linearity, limits of detection and quantification, accuracy, precision, selectivity, ruggedness and system suitability. The linearity of the method was excellent over the range 8–12 μg/ml. The mean values of slope, intercept and correlation coefficient were 1363, 3607 and 0.999 respectively. RSD in intra-day and inter-day precision studies was < 2 %. Recovery of oxybutynin from bulk drug ranged from 99.05 and 100.40 %. Oxybutynin was subjected to stress conditions (hydrolysis (acid, base), oxidation, photolysis and thermal degradation) and the stressed samples were analyzed by use of the method. Maximum degradation was observed in acid and base hydrolysis and oxidation. The drug was stable to degradation under photolytic and thermal conditions. The degradation products were well resolved from main peak thus proving the stability indicating nature of the method.

Keywords: oxybutynin; stability indicating; degradation products.