Anti-HIV drug combination that should not be used
Anti-HIV drug combinations that should NOT be used are:

Zidovudine + Stavudine: Pharmacological antagonism (compete for intracellular phosphorylation)
Atazanavir + Indinavir: Additive unconjugated hyperbilirubinemia.
Didanosine/stavudine + Zalcitabine: Additive peripheral neuropathy.
Lamivudine + Zalcitabine: In vitro antagonism.
Zidovudine + Stavudine
Atazanavir + Indinavir.
Didanosine/stavudine + Zalcitabine
All of the above.