Continuous infusion tobramycin combined with carbenicillin for infections in cancer patients

The cure rate of infections in cancer patients is adversely affected by neutropenia (less than 1,000/mm3). In particular, patients with severe neutropenia (less than 100/mm3) have shown a poor response to antibiotics. To overcome the adverse effects of neutropenia, tobramycin was given by continuous infusion and combined with intermittent carbenicillin. Tobramycin was given to a total daily dose of 300 mg/m2 and carbenicillin was given at a dose of 5 gm every four hours. There were 125 infectious episodes in 116 cancer patients receiving myelosuppressive chemotherapy. The overall cure rate was 70%. Pneumonia was the most common infection and 61% of 59 episodes were cured. Gram-negative bacilli were the most common causative organisms and 69% of these infections were cured. The most common pathogen was Klebsiella pneumoniae and this, together with Escherichia coli and Pseudomonas aeruginosa, accounted for 74% of all gram-negative bacillary infections. Response was not influenced by the initial neutrophil count, with a 62% cure rate for 39 episodes associated with severe neutropenia. However, failure of the neutrophil count to increase during therapy adversely affected response. Azotemia was the major side effect recognized, and it occurred in 11% of episodes. Major azotemia (serum creatinine greater than 2.5 mg/dl or BUN greater than 50 mg/dl) occurred in only 2%. Azotemia was not related to duration of therapy or serum tobramycin concentration. This antibiotic regimen showed both therapeutic efficacy and acceptable renal toxicity for these patients.