Evaluation of the Interaction Between Low Dose Sulfamethoxazole-Trimethoprim and Zidovudine

Inclusion Criteria Prior Medication: Allowed: Zidovudine (AZT) for patients with AIDS. AIDS related complex (ARC). The presence of any one of the following findings within 12 months prior to entry and the absence of a concurrent illness or conditions other than HIV infection to explain the findings: Fever of > 38.5 C degrees persisting for longer than 3 weeks. Involuntary weight loss of > 15 lbs. or > 10 percent of baseline noted in a 120-day period prior to evaluation. Diarrhea (> 2 liquid stools per day) persisting for longer than 1 month. History of clinical diagnosis of oral candidiasis or hairy leukoplakia. Patients who have AIDS-defining opportunistic infections or tumors. Patients eligible for AZT under the labeling. A positive HIV antibody test. Exceptions will be made for patients with a previously positive HIV antibody test with progressive disease and patients where virus isolation has been made. A life expectancy of at least 3 months. Patient with stable Kaposi's sarcoma, mild herpes infection, mild or stable depression, asymptomatic or mild cytomegalovirus or Epstein-Barr virus infection, or a hepatitis B virus carrier state will be acceptable for study. Exclusion Criteria Concurrent Medication: Excluded: Phenytoin. Prior Medication: Excluded within 30 days of study entry: Other antiretroviral agents. Patient has any severe ongoing opportunistic infections including Pneumocystis carinii pneumonia (PCP), cryptococcal or toxoplasmosis meningoencephalitis, disseminated herpes simplex or herpes zoster. Patient has significant diarrhea at entry ( > 1 watery stool per day). Patient has demonstrated prior sensitivity or has experienced significant adverse effects during prior therapy with the drugs to be used in the study. Cannot abstain from alcohol or any other drugs during the study.