Definition first pass metabolism
by Mike_B
first-pass metabolism n. a process in which a drug administered by mouth is absorbed from the gastrointestinal tract and transported via the portal vein to the liver, where it is metabolized. As a result, in some cases only a small proportion of the active drug reaches the systemic circulation and its intended target tissue. The first-pass metabolism or the first-pass effect or presystemic metabolism is the phenomenon which occurs whenever the drug is administered orally, enters the liver, and suffers extensive biotransformation to such an extent that the bioavailability is drastically reduced, thus showing subtherapeutic action (Chordiya et al., ). It happens when the drug is . FIRST PASS METABOLISM/ FIRSTPASS EFFECTS/ PRESYSTEMIC METABOLISM It is the phenomenon of drug metabolism. Where the concentration of a drug is greatly reduced before it reaches the systemic circulationFile Size: KB. Read more