[Studies on the competition of several antibiotics for binding sites to serum protein (author's transl)]

Abstract

Protein binding of benzylpenicillin, acidocillin, ampicillin, oxacillin, tetracycline and clindamycin was determined in vitro by equilibrium dialysis with and without combination. Concentrations of labelled drugs were measured by scintigraphy, of non-labelled drugs by agar diffusion technique using a test strain resistant against the second antibiotic of the combination. Percentage of protein binding of the different penicillins decreased somewhat in higher concentrations, whereas with tetracycline there was found a significant increase of protein binding in higher concentrations. There was no inhibition of protein binding when combining two penicillins or tetracycline with clindamycin at lower concentrations. If very high concentrations of oxacillin of flucloxacillin were used in combination with benzylpenicillin protein binding of benzylpenicillin was reduced by about 20%.