The toxicity of azidothymidine (AZT) in the treatment of patients with AIDS and AIDS-related complex. A double-blind, placebo-controlled trial.

We conducted a double-blind, placebo-controlled trial of oral azidothymidine (AZT) in 282 patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex. Although significant clinical benefit was documented (N Engl J Med 1987; 317:185-91), serious adverse reactions, particularly bone marrow suppression, were observed. Nausea, myalgia, insomnia, and severe headaches were reported more frequently by recipients of AZT; macrocytosis developed within weeks in most of the AZT group. Anemia with hemoglobin levels below 7.5 g per deciliter developed in 24 percent of AZT recipients and 4 percent of placebo recipients (P less than 0.001). Twenty-one percent of AZT recipients and 4 percent of placebo recipients required multiple red-cell transfusions (P less than 0.001). Neutropenia (less than 500 cells per cubic millimeter) occurred in 16 percent of AZT recipients, as compared with 2 percent of placebo recipients (P less than 0.001). Subjects who entered the study with low CD4 lymphocyte counts, low serum vitamin B12 levels, anemia, or low neutrophil counts were more likely to have hematologic toxic effects. Concurrent use of acetaminophen was also associated with a higher frequency of hematologic toxicity. Although a subset of patients tolerated AZT for an extended period with few toxic effects, the drug should be administered with caution because of its toxicity and the limited experience with it to date.