New developments in the clinical use of didanosine

Didanosine (ddI) is a purine analogue that demonstrates in vitro anti-human immunodeficiency virus (HIV) activity, effects on the surrogate markers CD4+ T-lymphocytes and p24 antigen, and has adequate oral bio-availability. Recently, 500 mg/day of ddI in sachet form demonstrated clinical effectiveness compared with zidovudine (ZDV) for delaying HIV disease progression in patients with AIDS or AIDS related complex (ARC) and less than 300 CD4+ T-lymphocytes, or asymptomatic individuals with less than 200 CD4+ T-lymphocytes. All patients tolerated a minimum of 16 weeks of prior ZDV treatment. ddI treatment was associated with an increase in serum amylase and pancreatitis, however, there was no significant difference in the incidence of pancreatitis between the 500 mg ddI and ZDV groups. There was significantly more hematologic toxicity associated with ZDV and no difference between ddI and ZDV groups with respect to peripheral neuropathy. ddI is presently available in tablet form with 125% the bioavailability of the sachet form of ddI; therefore, the 500-mg sachet formulation corresponds to a 400-mg daily tablet dose of ddI. Future studies of ddI will involve ddI's effects on antiretroviral naive patients and the potential of combining ddI with other agents.