Efficacy of Trimethoprim–Sulfamethoxazole for the Prevention of Bacterial Infections in a Randomized Prophylaxis Trial of Patients with Advanced HIV Infection

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Abstract
We compared the occurrences of several types of infections in HIV-infected patients participating in a randomized clinical trial of three treatment strategies given for the primary prevention of Pneumocystis carinii pneumonia (PCP) and toxoplasmosis. In a phase III open label trial, 842 patients with HIV infection and fewer than 200 CD4+ cells/mm(3) received zidovudine (standard dose) plus one of three randomly assigned prophylactic agents: trimethoprim-sulfamethoxazole (TMP-SMZ), or dapsone (DAP), or aerosolized pentamidine (AP). Patients developing intolerance to treatment were crossed over to another predefined prophylactic therapy. Patients were monitored for infections every other week for 8 weeks and then monthly until the study was completed. Primary statistical models were proportional hazards models adapted to recurrent end points. In an intent-to-treat analysis, compared with AP and DAP, TMP-SMZ significantly reduced the risk of any bacterial infection (combining all distinct types) (p = 0.02 and p = 0.01, respectively). When considering distinct types separately, compared with AP, TMP-SMZ significantly reduced the risk of infectious diarrhea (p = 0.04); compared with DAP, AP and TMP-SMZ significantly reduced the risk of sinusitis/otitis media (p = 0.03 and p = 0.04, respectively); compared with AP and DAP, TMP-SMZ significantly reduced the risk of a second occurrence of pneumonia (p = 0.04 and 0.02, respectively). For any bacterial infection, infection rates per 100 patient-years of follow-up were 31, 39, and 38 for TMP-SMZ, DAP, and AP, respectively. In patients with advanced HIV infection not taking highly active antiretroviral therapy, the treatment strategy that initiates prophylaxis with TMP-SMZ is superior to those initiating with AP or DAP for preventing any bacterial infection, with most of the advantage manifested through infectious diarrhea, sinusitis/otitis media, and pneumonia.