[Binding of sisomicin and gentamicin to serum proteins (author's transl)].

The binding of sisomicin and gentamicin to the proteins of human serum was investigated by the dialysis method at 37 degrees C. The antibiotic concentrations were determined by the disc diffusion assay as well as by measurements of the optical rotation of the antibiotics in the buffer solutions. Serum was dialyzed against buffer solutions to obtain the standards for the antibiotic assay with regard to the electrolytical exchange at dialysis. In studies on protein binding of sisomicin and gentamicin no measurable binding to human serum proteins could be found, neither in the therapeutically possible concentrations nor at higher ones. Therefore a different binding of the two antibiotics cannot be the reason of the advantage of sisomicin over gentamicin in tests in vivo with animals described in literature nor of its higher activity against several bacterial strains of different species tested in the presence of serum.