[Fundamental studies on combination of antibiotics; especially on pharmacokinetics. II. Combination of gentamicin and minocycline (author's transl)].

1. Minocycline (MNC) (10 mg/kg) and gentamicin (GM) (5 mg/kg), in combination with pre- or post-treatment, were intravenously injected to the rat or rabbit to investigate their pharmacokinetics. 2. The antibiotics in the samples were separated by the paper electrophoretic technique and their concentrations were determined by the cup thin-layer plate method using Bacillus subtilis as the test organism. 3. In the rat, the biological half life of MNC was shortened when combined with GM, and its initial level was elevated. On the other hand, the biological half life of GM was prolonged, and its initial level was decreased. Similar results were observed in the rabbit. 4. The urinary excretion rate of MNC in the rat was increased when combined with GM, while that of GM were decreased with MNC. 5. The biliary excretion rate of MNC in the rabbit was increased when combined with GM. 6. The binding rate of MNC to the serum proteins was apparently decreased when it was administered in combination with GM.