Medication Combo May Cause CD4-Cell Loss

Three studies presented at recent international conferences suggest that the combination of Viread and Videx EC (ddI) may result in an unexpected decline in CD4-cell counts. Researchers say that one study showed 51% of HIV patients taking 400 milligrams of ddI per day in combination with Viread experienced a CD4-cell decrease of at least 50 cells after one year of therapy, with a median decrease of 169 cells reported. When the dose of ddI was reduced to 250 milligrams, a progressive improvement in CD4-cell count was measured, with a median increase of 88 cells after 36 weeks. Two other studies also found CD4-cell drops in patients taking 400-milligram doses of ddI with Viread. The scientists say the potential mechanism causing the decline in immune system cells may be related to Viread's inhibitory effect on purine nucleoside phophorlyase, which helps break down ddI in the body. This results in high concentrations of ddI in the bloodstream and potential cellular damage. Taking lower doses of ddI can help reduce these blood-based concentrations, the studies suggest.