Objective: To determine the benefits of switching to didanosine compared with continuing zidovudine among patients infected with human immunodeficiency virus (HIV) who have previously used zidovudine and have signs of clinical deterioration.
Design: Randomized, double-blind, two-armed, parallel, comparative clinical trial with a blinded, compassionate crossover provision at 12 weeks.
Setting: Outpatient clinics at 19 tertiary care medical centers.
Patients: 312 patients infected with HIV who had received zidovudine for 6 months or more, had CD4 cell counts of 300/mm3 or less, and had signs of clinical deterioration within 12 weeks before study entry.
Intervention: Peroral didanosine tablets (600 mg/d adjusted for weight, “high dose”) or zidovudine capsules (600 mg/d).
Measurements: Primary study end points were death, a new acquired immunodeficiency syndrome (AIDS)-defining event, or the combination of two new or recurrent HIV-related diagnoses with a 50% decrease in CD4 cells.
Results: Switching to didanosine was associated with fewer end points than continuing zidovudine (relative risk [RR] for zidovudine:didanosine = 1.5; 95% CI, 1.1 to 2.0). This benefit was consistent across subgroups of patients with either AIDS-related complex or AIDS and was most apparent among those with a CD4 count at entry of 100/mm3 or more (RR = 2.2; CI, 1.1 to 4.4).
Conclusions: This study shows a positive treatment effect for switching from zidovudine to didanosine among patients with either AIDS-related complex or AIDS and validates the common practice of using clinical signs or a decrease in the CD4 count as an indication for changing therapy.
*For members of the Study Group, see the appendix.