Nafcillin-induced neutropenia in two children

Two cases of nafcillin-induced neutropenia in children are discussed. A seven-year-old girl was referred to the hospital after the pain and swelling in her foot persisted despite five days of oral penicillin VK therapy. Administration of intravenous nafcillin 150 mg/kg/day was started upon admission. The patient's leukocyte count was normal upon admission; further, her leukocyte and neutrophil counts were normal on the 10th and 17th days of hospitalization. After 22 days of nafcillin therapy, her leukocyte and neutrophil counts fell to 2300 and 162/cu mm, respectively. Three days after the nafcillin was discontinued, the leukocyte count was 5800/cu mm. The patient was given dicloxacillin 50 mg/kg/day, and had no recurrence of neutropenia. The second case involved a 28-month-old girl admitted to the hospital with fever, irritability, and skin rash. Her leukocyte count was normal upon admission. She received 10 days of penicillin G 100,000 units/kg/day, followed by 10 days of nafcillin 150 mg/kg/day, before neutropenia was discovered. On the ninth day of nafcillin therapy, here leukocyte and neutrophil counts were 4200 and 822/cu mm, respectively. Nafcillin was discontinued and cefazolin therapy was initiated at 100 mg/kg/day. Blood counts returned to normal, and there was no recurrence of neutropenia. Differential blood cell counts should be performed on patients receiving nafcillin, and, if neutropenia develops, nafcillin should be discontinued and treatment with a nonpenicillin antimicrobial considered.