To determine the safety, toxicity, pharmacokinetic profile, and antiretroviral activity of atevirdine mesylate ( U-87201E ) in HIV-infected patients. Per 06/04/93 amendment, to also evaluate the interactive effects of didanosine ( ddI ) or zalcitabine ( dideoxycytidine; ddC ) with zidovudine ( AZT ) on the pharmacokinetics of U-87201E and to assess the effects of the triple combination therapies on immunologic and virologic parameters.