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September 1965

Dicloxacillin: In Vitro and Pharmacologic Comparisons With Oxacillin and Cloxacillin

Author Affiliations


From the Department of Medicine, University of Washington School of Medicine. Trainees in Infectious Diseases (Drs. Gravenkemper and Bennett); Technologist (Miss Brodie); and Professor of Medicine (Dr. Kirby).

Arch Intern Med. 1965;116(3):340-345. doi:10.1001/archinte.1965.03870030020005

THE ISOXAZOLYL group of semisynthetic penicillins has been useful in the oral therapy of infections caused by penicillinase-producing staphylococci. Cloxacillin, which is available for general use in Great Britain instead of oxacillin, has in vitro activity similar to oxacillin against the common gram-positive pathogens and is superior to oxacillin in regard to blood levels obtained after oral and intramuscular administration.1-4 Another new isoxazolyl penicillin, dicloxacillin, appears to give even higher blood levels than cloxacillin, and the present report compares various in vitro and pharmacologic properties of dicloxacillin with those of oxacillin and cloxacillin.

Materials and Methods  Cloxacillin and dicloxacillin were supplied as the sodium monohydrate salt in 250 mg capsules and oxacillin as the sodium salt in 500 mg capsules, for oral administration.Susceptibility testing with standard powders of oxacillin, cloxacillin, and dicloxacillin was performed by a tube dilution method3 for at least ten recently isolated strains each