Trimethoprim-sulfamethoxazole and trimethoprim alone for prophylaxis of infection in granulocytopenic patients.

Prophylactic trimethoprim-sulfamethoxazole (TMP-SMZ) has been shown to reduce the incidence of fever, parenteral antibiotic usage, and infections with gram-negative bacteria in hospitalized patients with neutropenia. Furthermore, TMP-SMZ was found to be equivalent to or better than oral, nonabsorbable antibiotics in direct comparisons and to have an additive effect when given together with other oral, nonabsorbable antibiotics. Adults given TMP-SMZ continuously had fewer readmissions for infection than did controls given TMP-SMZ only while hospitalized. TMP-SMZ used continuously in children with acute leukemia was effective in preventing bacterial and Pneumocystis carinii infections. For prophylaxis in granulocytopenic patients, TMP appeared equivalent to TMP-SMZ both in efficacy and incidence of side effects. However, TMP was less effective in suppressing gastrointestinal flora, including TMP-resistant gram-negative rods. Thus, TMP-SMZ has some role in preventing infections in high-risk patients, but further studies, especially comparisons with untreated patients may still be required. TMP used alone offers little advantage and has the theoretical disadvantage of not preventing infections caused by P. carinii or TMP-resistant gram-negative bacteria.