Infectious Diseases

The acquired immunodeficiency syndrome (AIDS) epidemic continues to dominate the subspecialty of infectious diseases. New basic science and clinically relevant data about AIDS continue to rapidly accumulate. Zidovudine (formerly named azidothymidine [AZT]) remains the only available agent for treatment of AIDS, but its effect is limited in duration. One long-suspected explanation is the development of resistance to zidovudine by the human immunodeficiency virus (HIV). Larder and coworkers¹ tested the sensitivity of HIV isolates to zidovudine in patients who had received zidovudine therapy. Most isolates obtained after 6 months or more of therapy were less sensitive than those obtained before or during the first few months of therapy. Although not proven, it is plausible that drug resistance may play a role in diminished clinical effectiveness of zidovudine after several months of therapy. If true, this finding could provide a strong argument for the use of drug combinations, either simultaneously or