title: Down the hatch: is prescribing medication really that simple?
abstract: Drug absorption and metabolism is influenced by age, sex, pharmacogenetic variability, medical comorbidity, concurrent drug use, drug formulation, and route of administration. Drug dissolution typically begins in the stomach, but absorption occurs mainly in the small intestine. Malabsorption syndromes, previous gastrointestinal (GI) surgery, or decreased GI blood flow impair or delay the absorption of orally administered drugs. Decreased drug absorption can occur with certain gastric bypass procedures when the stomach or proximal small intestine is an important absorption site. Drugs undergoing extensive first-pass hepatic metabolism can have increased concentrations and greater systemic effects when administered directly into the jejunum. Non-oral routes of drug administration ordinarily bypass first-pass hepatic metabolism, leading to greater bioavailability and higher concentrations compared with oral administration of the same dose. Metabolic activity is variably reduced with increased age or liver disease severity, but declines in liver function cannot be quantified to determine drug metabolizing capacity.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Howland
mesh_terms: D000367:Age Factors; D001682:Biological Availability; D002626:Chemistry, Pharmaceutical; D004333:Drug Administration Routes; D005260:Female; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology*; D008297:Male; D055553:Prescription Drugs / Q000008:administration & dosage* / Q000378:metabolism*; D011619:Psychotropic Drugs / Q000008:administration & dosage* / Q000493:pharmacokinetics*; D012737:Sex Factors
chemical_list: D055553:Prescription Drugs; D011619:Psychotropic Drugs