title: A mechanistic approach to understanding the factors affecting drug absorption: a review of fundamentals.
abstract: This article provides an overview of the patient-specific and drug-specific variables that can affect drug absorption following oral product administration. The oral absorption of any chemical entity reflects a complex spectrum of events. Factors influencing product bioavailability include drug solubility, permeability, and the rate of in vivo dissolution. In this regard, the Biopharmaceutics Classification System has proven to be an important tool for predicting compounds likely to be associated with bioavailability problems. It also helps in identifying those factors that may alter the rate and extent of drug absorption. Product bioavailability can also be markedly influenced by patient attributes such as the integrity of the gastrointestinal tract, physiological status, site of drug absorption, membrane transporters, presystemic drug metabolism (intrinsic variables), and extrinsic variables such as the effect of food or concomitant medication. Through an awareness of a drug's physicochemical properties and the physiological processes affecting drug absorption, the skilled pharmaceutical scientist can develop formulations that will maximize product availability. By appreciating the potential impact of patient physiological status, phenotype, age, gender, and lifestyle, dosing regimens can be tailored to better meet the needs of the individual patient.
authors.affiliation: Office of New Animal Drug Evaluation, Center for Veterinary Medicine, Food and Drug Administration, Rockville, Maryland 20855, USA.
authors.forename: Marilyn N
authors.initials: MN
authors.lastname: Martinez
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Amidon
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000502:physiology; D018528:ATP-Binding Cassette Transporters / Q000502:physiology; D001682:Biological Availability; D002352:Carrier Proteins / Q000502:physiology; D004058:Diffusion; D005502:Food; D007408:Intestinal Absorption; D050356:Lipid Metabolism; D000074011:Peptide Transporter 1; D010599:Pharmacokinetics; D012995:Solubility; D027981:Symporters
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D000074011:Peptide Transporter 1; D027981:Symporters