Neutropenia associated with beta-lactam antibiotics

Two patients who developed neutropenia while receiving beta-lactam antibiotics are presented, and the literature on beta-lactam-induced neutropenia is reviewed. A 55-year-old white woman was admitted to the hospital with a white blood cell (WBC) count of 8700/cu mm (68% neutrophils, 12% neutrophil bands, 0% eosinophils, 14% lymphocytes, 5% monocytes). Moxalactam 2 g i.v. (as the disodium salt) every eight hours was started on hospital day 15 after a postoperative fever failed to respond to a regimen of intravenous tobramycin and clindamycin. The patient again had surgery on hospital day 27, and the moxalactam regimen was continued postoperatively. Approximately one week later the patient's WBC count had dropped to 1900/cu mm (8% neutrophils, 14% neutrophil bands, 6% eosinophils, 54% lymphocytes, 16% monocytes); moxalactam was discontinued, and the WBC count gradually increased after substitution of tobramycin and clindamycin for moxalactam. The second patient was a 75-year-old white man who was being treated with intravenous tobramycin and cefoxitin for a hospital-acquired pneumonia. Ticarcillin 3 g i.v. (as the disodium salt) every four hours was added to this regimen on hospital day 23 after sputum cultures revealed Pseudomonas aeruginosa; four days previously, the WBC count had been 25,100/cu mm (64% neutrophils, 31% neutrophil bands, 1% eosinophils, 3% lymphocytes, 0% monocytes). The WBC count on hospital day 36 was 11,900/cu mm (39% neutrophils, 33% neutrophil bands, 11% eosinophils, 10% lymphocytes, 6% monocytes). Two days later it had dropped to 3700/cu mm (2% neutrophils, 0% neutrophil bands, 53% eosinophils, 24% lymphocytes, 16% monocytes), and ticarcillin was discontinued. The WBC count gradually increased and returned to normal within three days after discontinuing ticarcillin. Neutropenia associated with the administration of beta-lactam antibiotics appears to result from an immunologic reaction characterized by rapid destruction of peripheral neutrophils. Among penicillin analogs, penicillinase-resistant penicillins are involved most frequently, especially in pediatric patients receiving dosages of 150 mg/kg/day or greater. Two case reports have implicated ticarcillin as a cause of neutropenia; moxalactam has not been associated with this adverse effect in previous literature reports. Discontinuation of the suspected agent and initiation of an alternative antibiotic regimen is recommended as initial treatment of this condition since recovery usually occurs within days after discontinuing the offending drug.