Combination Therapy with ZDV + DDI Versus ZDV + DDC in Patients with Progression of HIV-Infection Under Treatment with ZDV

HIV-seropositive patients (n = 67) who had tolerated zidovudine for at least 24 weeks and deteriorated clinically or immunologically within 12 weeks prior to study entry were allocated in an alternating manner to didanosine chewable tablets (400 mg/day) plus zidovudine (500 mg/day) or dideoxicytidine capsules (2.25 mg/day) plus zidovudine (500 mg/day). The combination of didanosine and zidovudine resulted in a more pronounced increase of CD4 cells over time compared to the combination of dideoxicytidine with zidovudine (p < 0.002). The increase of CD4 cells was almost exclusively due to patients with more than 100 CD4 cells/microliters. Clinical end points (death, AIDS-defining disease, CDC IV event) were less frequent under didanosine plus zidovudine but failed to reach statistical significance (p = 0.07). For didanosine plus zidovudine the median time on medication during study was shorter (63% vs. 100%, p < 0.05) and the number of patients discontinuing medication prematurely due to side effects was higher (59% vs. 30%, p < 0.02). The present study favors the combination of didanosine and zidovudine in patients deteriorating while receiving zidovudine for > 24 weeks in respect to the time course of the CD4 cells. In this small sized study, there seemed to be fewer clinical events in patients on the didanosine combination compared to the combination with dideoxicytidine; however, this trend failed to reach statistical significance and needs therefore to be substantiated by larger studies. However, the lower compliance of the patients may hamper the efficacy of didanosine.