DEVELOPMENT OF A VALIDATED STABILITY-INDICATING METHOD FOR ESTIMATION OF ETHIONAMIDE IN TABLETS BY RP-HPLC AND CHARACTERIZATION OF ITS ISOLATED ALKALI DEGRADATION PRODUCT

A simple, accurate, reproducible and specific stability-indicating RP-HPLC method was developed for estimation of ethionamide in tablets. Ethionamide was exposed to acid, alkali and neutral hydrolysis at elevated temperatures, to thermolytic degradation, peroxide-mediated oxidation at room temperature in dark and to photolytic degradation. The drug was found stable to thermolytic and photolytic conditions and to neutral hydrolysis. However, substantial degradation was obtained in acid and alkali hydrolysis and complete degradation in peroxide-medicated oxidation. Similar degradation behavior was observed when ethionamide tablets were exposed to the mentioned forced degradation conditions. The method showed adequate resolution of drug from its potential degradation products on C18 (250 × 4.6 mm, 5µ) column using mobile phase of methanol: water (50: 50 % V/V) at 1 mL/min. The drug and its potential degradation products were detected at 290 nm. The method was validated as per the ICH Q2(R1) guidelines. The enrichment of the alkali degradation product was performed and isolated by preparative TLC and further confirmed by NMR and IR spectroscopy