title: Theoretical relationships between area under the curve and route of administration of drugs and their precursors for evaluating sites and pathways of metabolism.
abstract: The bioavailability of a drug administered extrasystemically is a measure of the initial extraction of a compound by a series of eliminating events involving the intestinal mucosal enzymes, the gut bacterial microflora, the liver, and the lung. A theoretical analysis is presented to differentiate the process of gut wall elimination and hepatic removal of a drug during this first-pass effect. The area under the blood concentration--time curve (AUC) for a drug and its metabolite is shown to be useful in determining the presence of these processes when a drug and its metabolite are administered concomitantly by different routes of administration. Furthermore, the fraction of a precursor transformed to its metabolite also can be determined by pharmacokinetic analysis of the AUC of a drug and its metabolite after administration of both substances.
mesh_terms: D001682:Biological Availability; D007413:Intestinal Mucosa / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008954:Models, Biological; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004364:Pharmaceutical Preparations