title: Estimate of volume/flow ratio of gastrointestinal (GI) fluids in humans using pharmacokinetic data.
abstract: Based on the mixing tank and tube models for drug absorption, the apparent absorption rate constant is shown to be related to the fraction of dose absorbed as a function of the volume/flow ratio of GI fluids. This analysis applies to drugs that are absorbed according to first-order kinetics, without limitation by dissolution rate, lumenal decomposition, or first-pass metabolism. Analysis of pharmacokinetic data of drugs that fit these criteria and are absorbed to varying extents enabled the estimation of the volume/flow ratio of GI fluids in humans; it was found to be 1.6 +/- 0.3 (SE) hr using a mixing tank model and 0.32 +/- 0.05 hr using a tube model. These findings are discussed with respect to volume and flow parameters used in the design of various types of drug absorption studies.
authors.affiliation: Department of Pharmacy, University of Athens, Greece.
authors.forename: P
authors.initials: P
authors.lastname: Macheras
authors.forename: C
authors.initials: C
authors.lastname: Reppas
authors.forename: J B
authors.initials: JB
authors.lastname: Dressman
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D004064:Digestive System / Q000378:metabolism*; D005772:Gastrointestinal Transit; D006801:Humans; D007408:Intestinal Absorption; D008432:Mathematical Computing; D008954:Models, Biological; D010599:Pharmacokinetics; D051381:Rats