Rates and risk factors for adverse events associated with didanosine in the expanded access program

The didanosine Expanded Access Program was the largest AIDS treatment program to prospectively evaluate the safety of an antiretroviral agent among patients with advanced human immunodeficiency virus (HIV) disease in whom therapy with zidovudine was failing. A total of 21,198 patients who had infections refractory to zidovudine or who were intolerant of the drug received didanosine as a buffered powder for oral solution (sachet), with total daily doses of 6.6-10 mg/kg; the median CD4 lymphocyte count was 0.04 x 10(9)/L for this population. At the currently recommended dose (6.6-8.29 mg/[kg.d]), 6-month estimated rates of pancreatitis ranged from 1.2% for patients with AIDS-related complex (ARC) and CD4 lymphocyte counts of > or = 0.1 x 10(9)/L to 6.7% for patients with AIDS and CD4 lymphocyte counts of < 0.05 x 10(9)/L. Laboratory toxicities of World Health Organization grades 3 and 4 developed in fewer than 4% of patients entering the study with normal baseline values; the sole exception was leukopenia, which was documented in 8% of these patients. The results of this program demonstrated that patients with CD4 lymphocyte counts of < 0.10 x 10(9)/L or with a diagnosis of AIDS (defined by the 1987 classification system of the Centers for Disease Control and Prevention) were less tolerant of didanosine and significantly more likely to develop adverse clinical reactions and myelosuppression than other patients.