The Antibacterial Action of Erythromycin.

Abstract

Erythromycin solns. were stable in the cold but deteriorated progressively with increased temps. Filtration entailed some loss of activity. Activity of erythromycin increased progressively with increasing alkalinity of culture medium within the pH range of bacterial growth. Erythromycin-inhibiting substances could not be demonstrated in cultures of erythromycin -resistant bacteria. Tests done on more than 1000 bacterial strains, most of them recently isolated from patients, indicated that erythromycin was most active against Gram-positive cocci, quite active against Neisseria bacilli and Hemophilus and was essentially inactive against most coliform and enteric bacilli. After single oral doses, conens. of erythromycin varied widely, but were generally in proportion to the dose. Max. conens. were found 1 or 2 hrs. after a dose and no activity was demonstrated at 6 hrs. except following doses of 1.0 g. Significant conens. were maintained in plasma with oral doses of 250 mg. or more every 3 or 4 hours. Urinary recoveries were erratic after single oral doses or after small repeated doses particularly early in the course of therapy; continuous therapy with divided doses yielded up to 15% of the ingested daily dose in an active form in the urine.