Zidovudine plus didanosine in HIV infected asymptomatic patients previously treated with zidovudine

OBJECTIVE: To evaluate if the combination of AZT/ddl offered any advantages in surrogate markers among HIV infected asymptomatic patients previously treated with AZT for at least six months. METHODS: We used a prospective cohort of 269 asymptomatic HIV patients with CD4+ cell counts between 200 and 500 cells/microL. They were given didanosine (ddl 400 mg/d) in addition to AZT (500 mg/d) and had received AZT monotherapy for an average of 20 months. End points were progression to AIDS, death, or toxicity. RESULTS: Median CD4+ cell count at the start of the combination therapy was 339 cells/microL which increased at three months to 451 and subsequently declined at 6, 12 and 18 months of followup (medians of 392, 360, 307 cells/microL respectively). Five patients progressed to AIDS, six developed toxicity (myelosuppression, hepatitis or pancreatitis) and 26 had minor side effects that required only dose reduction. CONCLUSIONS: The addition of ddl to patients with prolonged ZDV monotherapy can be useful. CD4+ T cell counts showed a significant increase at 3 months with a gradual subsequent decline to below baseline at 18 months. Adverse effect of the drugs, although frequent, did not stop therapy in most patients.