Consequences of diarrhoeal disease on the pharmacokinetics of norfloxacin.

The pharmacokinetics of 400 mg norfloxacin administered orally were studied in 19 patients both during the acute phase of bacterial gastroenteritis and during convalescence, after normalization of bowel movements. The peak serum concentrations, total area under the serum concentration curve, rate of elimination and serum half-life in the beta-phase were all similar during the acute phase of the disease as well as after normalization of the intestinal function. The only difference was that the time to peak concentrations was longer (p less than 0.01) during the acute phase of the disease. That finding suggests that the faster intraintestinal transport of the drug during the acute stage of the disease leads to a reduced efficiency of early absorption. However, since the bioavailability was not affected, norfloxacin is obviously absorbed at a lower intestinal level and no dose adjustment should be necessary in patients with diarrhoea.