[Biologic availability of caffeine in subjects with regard to the variability of the elimination half life].

400 mg of caffeine and sodium salicylate (= 220 mg of caffeine) were given orally and intravenously (at an interval of one week) to six test persons. The serum levels were determined; and certain pharmacokinetic parameters were measured, using an open one-compartment model. Finally, the absolute bioavailability was calculated. With one of the test persons this experiment was repeated ten times to evaluate the extent of the intra-individual variability of the half-life period and its repercussions on bioavailability.