[Activity in vitro and pharmacokinetics of minocycline (author's transl)]. / In-vitro-Aktivität und Pharmakokinetik von Minocyclin

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.

[The pharmacokinetics of doxycycline in kidney insufficiency in geriatric patients compared to younger adults]. / Die Pharmakokinetik von Doxycyclin bei Niereninsuffizienz und geriatrischen Patienten im Vergleich zu jüngeren Erwachsenen

In young adults i.v. injection of 200 mg doxycycline was followed by a rapid fall in serum levels in the first 30 minutes and than a slow decrease (serum concentration after 24 h on average 1.0 mug/ml). Biological half-life was 11.9 h, final distribution volume 50.0 litres and urine recovery 70%. After oral administration of 200 mg doxycycline the serum peaks measured were 3.4 mug/ml (2 1/2 h later). With repeated doses of 100 mg every 24 h serum peaks were 2.8 mug/ml and serum concentrations after 24 h 0.8-0.9 mug/ml (urine recovery 43%). The area under the curve was 25.5% less than after i.v. injection. In 7 adults with chronic renal failure the half-life of doxycycline varied between 10 and 24 h. With repeated oral administration of doxycycline (100 mg every 24 h) there was no accumulation of the drug in blood. During hemodialysis (Stuttgart kidneys, Rhône-Poulenc plates) doxycycline injected i.v. was eliminated as rapidly as before. In renal failure doxycycline may be given in the same dosage as where renal function is normal. In 12 geriatric patients without renal disease, serum levels of doxycycline after i.v. injection of 200 mg were not significantly different from those of young adults (distribution volume 46.2 +/- 16.2 litres). It can therefore be assumed that tissue penetration of the drug is similar in the elderly and in young adults.