[Activity in vitro and pharmacokinetics of minocycline (author's transl)]

The in vitro activity of doxycycline and minocycline (Klinomycin) was determined by serial dilution test in 100 strains of E. coli, 101 strains of enterobacter, 91 tetracycline-sensitive and 52 tetracycline-resistant strains of staphylococci. Only staphylococci were more sensitive against minocycline than against doxycycline whereas other species showed nearly the same sensitivity against both antibiotics. After i.v. infusion of 200 mg minocycline (during 1 h) mean serum levels fell from 3.5 mug/ml to 0.6 mug/ml (after 24 h). Half-life was calculated as 15.7 h, urine recovery as 5.9%. After oral application of 200 mg minocycline serum level peaks were 2.7 mug/ml, serum levels after 24 h 0.7 mug/ml. At repeated administrations daily dosage of 100 mg was too low of 200 mg sufficient to obtain the same serum levels as after the initial dose of 200 mg. CSF levels after oral administration of 0.4 g minocycline were 0.74 +/- 0.09 mug/ml (in serum at the same time 2.2 +/- 0.2 mug/ml). Half-life of minocycline in chronic renal failure (7 adult patients) was not prolonged (15--20 h). Minocycline is especially suitable for treatment of infections of unknown bacterial origin (including such caused by staphylococci). I.v. infusion is indicated only in unconscious or vomiting patients.