title: Mechanistic understanding of time-dependent oral absorption based on gastric motor activity in humans.
abstract: The relationship of gastric motor activity and gastric emptying of 0.7 mm caffeine pellets with their absorption was investigated in the fed state in healthy human subjects by simultaneous monitoring of antral motility and plasma concentrations. A kinetic model for gastric emptying-dependent absorption yielded multiple phases of gastric emptying and rate constants (k(g)) with large inter-individual differences and large variability in onset of gastric emptying (50-175 min). The model suggests that 50% of the dose is emptied in 1-2h and over 90% emptied by 3.5h following dosing, in all subjects. The maximum values of k(g) (k(g)(max)) were much greater than those reported for emptying of liquids in the fasted state and were comparable to k(g) values in the late Phase II/III of the migrating motor complex (MMC). The model described the observed irregular absorption rate-time and plasma concentration-time profiles adequately but not in detail. The model was more successful at simulating double-peak phenomena in absorption rate profiles and onset of caffeine absorption. The results suggest that gastric emptying regulates drug absorption of small particles in the fed state. Further, estimates of k(a) derived using the time-dependent absorption model were closer to the intrinsic absorption rate constant for caffeine.
authors.affiliation: College of Pharmacy, The University of Michigan, Ann Arbor, MI 48109, USA.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Higaki
authors.forename: Sally Y
authors.initials: SY
authors.lastname: Choe
authors.forename: Raimar
authors.initials: R
authors.lastname: Löbenberg
authors.forename: Lynda S
authors.initials: LS
authors.lastname: Welage
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Amidon
mesh_terms: D000284:Administration, Oral; D000328:Adult; D002110:Caffeine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D005746:Gastric Emptying; D005769:Gastrointestinal Motility; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008954:Models, Biological; D016065:Myoelectric Complex, Migrating; D019518:Postprandial Period; D011706:Pyloric Antrum / Q000502:physiology*; D013608:Tablets, Enteric-Coated
chemical_list: D013608:Tablets, Enteric-Coated; D002110:Caffeine