Pharmacokinetics of doxycycline polyphosphate after oral multiple dosing in humans.

Nine healthy volunteers received oral multiple doses of doxycycline polyphosphate for 6 days. Three different dosage schedules were given and the time concentration data obtained was used to determine the best protocol for producing effective serum antibiotic levels during a complete period of treatment with the aid of a mathematical simulation programme. This protocol consisted of the administration of a 200 mg loading dose on the first day, followed by a 100 mg maintenance dose every twelve hours. Using this dosage schedule a steady state was obtained on the first day of treatment, 3 mg/l was the maximum serum level reached, and the lowest serum concentration was more than 1 mg/l which was assumed to be a therapeutically effective serum concentration.