Validated specific HPLC method for determination of zidovudine during stability studies

The objective of the current study was to develop a validated stability-indicating assay method (SIAM) for zidovudine (3'-azido-3'-deoxythymidine) after subjecting it to forced decomposition under hydrolysis, oxidation, photolysis and thermal stress conditions. The drug decomposed under hydrolytic stress upon refluxing, and also on exposure to light. It was stable to oxidation and thermal stress. The same major decomposition product could be seen in all the decomposed solutions, which was identified as thymine through comparison with the standard. Separation of drug from major and minor degradation products was successfully achieved on a C-18 column utilising water-methanol in the ratio of 77:23. The detection wavelength was 265 nm. The method was validated and response was found to be linear in the drug concentration range of 25-500 microg ml(-1). The mean values (+/-R.S.D.) of slope and correlation coefficient were 21,859 (+/-0.213) and 0.9995 (+/-0.00578), respectively. The R.S.D. values for intra- and inter-day precision were <0.9 and <1.6%, respectively. The method was established to have sufficient intermediate precision as similar separation was achieved on another instrument handled by a different operator. The recovery of the drug from a mixture of degraded samples ranged between 100.6 and 100.9%. PDA peak purity test confirmed the specificity of the method. The method was also successful in analysis of drug in marketed tablets subjected to stability testing under accelerated conditions of temperature, humidity, and to thermal and photolytic stress.