Mecillinam and ampicillin separately or combined in gram-negative septicemia.

Of 20 patients with gram-negative septicemia treated with mecillinam alone or in combination with ampicillin, successful therapeutic results were obtained in 16. In 11 patients treated with ampicillin alone, three failures responded successfully to a combination of mecillinam and ampicillin. Mecillinam MIC values of isolated Enterobacteriaceae were 0.05-0.4 micrograms/ml. In patients receiving 5 mg/kg mecillinam intravenously every six hours, the mean 0.5 hour concentration was 11.0 micrograms/ml and in those given 10 mg/kg 23.3 migcrograms/ml. No serious side effects were recorded. One patient on mecillinam developed an exanthema, as did three patients on combined therapy.