Preliminary Report Comparing Piperacillin and Carbenicillin for Complicated Urinary Tract Infections

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Abstract
Piperacillin is a new semisynthetic penicillin with a broad spectrum of in vitro activity against common gram-negative urinary tract pathogens. The efficacy and safety of piperacillin vs. carbenicillin were compared in patients with complicated urinary tract infection. A total of 56 adult patients (mean age 55 yr) in stable medical condition with 1 or more structural genitourinary abnormalities entered the study. Of these patients, 27 were evaluated for antibiotic efficacy. There were 20 lower tract and 7 upper tract infections, of which 17 were acute and 10 were chronic. Patients were randomized into 2 groups: 17 patients with 18 organisms received single agent treatment with 181 mg/kg i.v. piperacillin daily for 6 days and 10 patients with 11 organisms received 270 mg/kg i.v. carbenicillin daily for 6 days. Infecting organisms were Escherichia coli 45%, Proteus mirabilis 14%, Klebsiella pneumoniae 14%, Enterobacter spp. 10%, Pseudomonas aeruginosa 7%, etc. Antimicrobial susceptibility assessed by measurement of minimal inhibitory concentration and disk diffusion zone size demonstrated superior activity of piperacillin over carbenicillin for most microorganisms tested. All patients responded clinically. The bacteriologic cure rate was 72% at 5-9 days after therapy in both groups. Three patients who received piperacillin had urosepsis and were cured. No resistance emerged during therapy. Superinfections developed in 5 patients on carbenicillin (50%) and in 4 patients on piperacillin (24%) and none was resistant to piperacillin. Superinfections were attributed to catheterization and structural genitourinary abnormalities. The overall incidence of adverse effects in patients on piperacillin was less than that of those on carbenicillin, 31 and 51%, respectively. Side effects in both groups were mild and did not require discontinuation of therapy. There were no significant alterations in fluid and electrolyte balance, or hematologic or renal function.