title: Estimation of the extent of oral absorption in animals from oral and intravenous pharmacokinetic data in drug discovery.
abstract: Oral administration is the most desirable route of drug delivery for systemically active drugs. Oral drugs must possess a certain level of oral bioavailability, which is a product of oral absorption and first-pass effect. Low oral bioavailability may be attributed to poor absorption and/or high first-pass hepatic elimination. In the lead optimization stage of drug discovery, if the relative contribution of oral absorption and metabolism could be discerned for poorly bioavailable compounds, a path forward for remedy would be possible. This report describes an approach utilizing oral/intravenous pharmacokinetic data to estimate oral absorption. The fraction of dose absorbed is calculated as the ratio of the actual bioavailable fraction to the maximum bioavailable fraction estimated from systemic clearance. An arbitrary classification was devised where low absorption encompasses compounds whose extent of absorption is <or=20%, moderate is for those between 21% and 69%, and high is for those that show >or=70% absorption. There was approximately 78% concordance in rats, 65% in monkeys and almost complete concordance in dogs. This approach correctly identified the cause for low oral bioavailability for 11 out of 13 compounds evaluated, and therefore it could be used prospectively with nonradiolabeled compounds during the lead optimization process.
authors.affiliation: Department of Drug Metabolism and Pharmacokinetics, Schering-Plough Research Institute, Mail Stop 2880, Kenilworth, New Jersey 07033, USA. amin.nomeir@spcorp.com
authors.forename: Amin A
authors.initials: AA
authors.lastname: Nomeir
authors.forename: Richard
authors.initials: R
authors.lastname: Morrison
authors.forename: Daniel
authors.initials: D
authors.lastname: Prelusky
authors.forename: Walter
authors.initials: W
authors.lastname: Korfmacher
authors.forename: Lisa
authors.initials: L
authors.lastname: Broske
authors.forename: David
authors.initials: D
authors.lastname: Hesk
authors.forename: Paul
authors.initials: P
authors.lastname: McNamara
authors.forename: Hong
authors.initials: H
authors.lastname: Mei
mesh_terms: D000042:Absorption; D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D001682:Biological Availability; D055598:Chemical Phenomena; D004285:Dogs; D055808:Drug Discovery; D004353:Drug Evaluation, Preclinical; D007275:Injections, Intravenous; D008252:Macaca fascicularis; D008297:Male; D008657:Metabolic Clearance Rate; D008970:Molecular Weight; D004364:Pharmaceutical Preparations / Q000737:chemistry / Q000378:metabolism*; D010599:Pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D014018:Tissue Distribution
chemical_list: D004364:Pharmaceutical Preparations