Mezlocillin for treatment of infections in cancer patients.

Mezlocillin, at a dose of 3 g intravenously over a 2-h period every 4 h, was used for the treatment of 92 episodes of documented infections in 75 myelosuppressed cancer patients. The response rate in 59 evaluable bacterial infections was 46%. Eight of 23 patients with septicemia (35%) responded. The response rates for Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli, the three most common gram-negative infections, were 42, 64, and 70%, respectively. Mezlocillin was well tolerated; the only toxicity attributable to this antibiotic was a skin rash in one patient. The formation of a false-positive urine protein reaction by mezlocillin was noted. This study demonstrated that mezlocillin administered as a single agent was effective against some infections in myelosuppressed cancer patients. The response rate for Klebsiella sp. infections was especially encouraging. However, because it had limited or little activity against many infections, especially those caused by P. aeruginosa and Staphylococcus aureus, the general use of mezlocillin as a single agent for treatment of infections in immunocompromised cancer patients cannot be recommended.