The following anti-HIV drug should not be combined with zidovudine because of mutual antagonism

Stavudine (d4T) It is also a thymidine analogue which acts by utilizing the thymidine kinase for activation, AZT(zidovudine) antagonises the effect of stavudine and the two should not be used together. It should also not be combined with didanosine, because both cause peripheral neuropathy. side effects:- Frequent peripheral neuropathy, lipodystrophy, lactic acidosis, and rarely pancreatitis are noted. Ref:- kd tripathi; pg num:-807