PAT 20A/B Study Guide - Midterm Guide: Hepatic Portal System, Gastrointestinal Tract, Portal Vein
5 Jan 2017
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Document Summary
Patho phases of pharmacokinetics: movement of a drug from its site of administration into bloodstream for distribution to the tissues, when drug moves into bloodstream, bioavailability: extent of drug absorption ( before it reaches systemic circulation) . Usually oral administered drugs have bioavailability of less than 100% because of the first pass effect. Intravenous drugs are 100% bioavailable: first-pass effect: . Orally administered drugs: absorbed from the gi tract, carried to liver via hepatic portal circulation. Liver metabolizes the drug before reaching systemic circulation. Large amounts may be inactivated leading to therapeutic effects. Some of the active drug gets inactivated/diverted before it can reach the general circulation and to the sites of action. Only occurs when drug is administered orally the drug goes through the venous portal system to liver and gets metabolized by the liver and excreted in bile. This reduces bioavailability of the drug bc it decreases the conc. of the drug.
