Intravenous trimethoprim-sulfamethoxazole alone or combined with tobramycin for infections in cancer patients.

A total of 120 episodes of infection in 113 cancer patients were treated with intravenous trimethoprim-sulfamethoxazole (TMP-SMX) alone (92 episodes) or with TMP-SMX plus continuous infusion tobramycin (28 episodes). The overall response rates were 47% and 75%, respectively. The majority of episodes had failed to respond to prior antibiotics. Pneumonia was the most common infection, and Klebsiella pneumoniae was the most common pathogen. TMP-SMX plus tobramycin cured 86% of episodes of septicemia and 76% of episodes of pneumonia, whereas TMP-SMX alone cured 20% and 42%, respectively. The initial neutrophil count did not appear critical in determining the outcome of infection. It was the change in the neutrophil count during the infection that appeared important. The outcome of infection was less favorable where abnormal renal and/or hepatic functions were documented. The sensitivity of the organism in vitro to TMP-SMX and/or tobramycin correlated well with the in vivo response. Intravenous TMP-SMX was well tolerated with a 4% incidence of reversible toxicity. A 15% incidence of renal toxicity was attributable to tobramycin. Intravenous TMP-SMX appears to be useful antimicrobial regimen for the therapy of infections caused by susceptible organisms in cancer patients.