The ICH guidance in practice: stress degradation studies on ornidazole and development of a validated stability-indicating assay

The present study describes degradation of ornidazole under different ICH prescribed stress conditions (hydrolysis, oxidation and photolysis), and establishment of a stability-indicating reversed-phase HPLC assay. Degradation was found to occur in alkaline medium, under high acidic conditions, under oxidative stress, and also in the presence of light in acid conditions. Previously the drug is only known to decompose under alkaline conditions. Separation of drug and the degradation products under various conditions was successfully achieved on a C-18 column utilising water-acetonitrile in the ratio of 86:14. The detection wavelength was 310 nm. The method was validated with respect to linearity, precision, accuracy, selectivity, specificity and ruggedness. The response was linear in the drug concentration range of 5–500 μg ml⁻¹. The mean values (±RSD) of slope, intercept and correlation coefficient were 45251 (±1.59), 104418 (±2.49) and 0.9996 (±0.03), respectively. The RSD values for intra- and inter-day precision studies were <1 and <2.6%, respectively. The recovery of the drug ranged between 100–103% from a mixture of degradation products. The method was specific to drug and also selective to degradation products.