Comparative Toxicities of Methicillin and Nafcillin

In a prospective, randomized study, 75 infants and children were treated with methicillin sodium and 74 were treated with nafcillin sodium. The two groups were comparable with regard to age, sex, duration of therapy, types of illnesses, etiologic bacteria, and bacteremia. Clinical responses were also comparable. The frequencies of fever, rash, eosinophilia, neutropenia, anemia, and abnormal hepatic enzymes were the same in the two groups. Two patients in each group had transient hematuria early in their course that resolved despite continued antibiotic therapy. Definite urologic toxic effect did not occur in patients who received nafcillin, while four (5.3%) of the methicillin-treated patients were judged to have this complication. In addition, six patients (8%) who received methicillin had questionable evidence of urologic toxic effect. It is concluded that methicillin and nafcillin have comparable clinical efficacy and adverse effects, with the exception that definite urologic toxic effect has been observed with nafcillin therapy.