The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation. It is the fraction of drug lost during the process of absorption which is generally related to the liver and gut wall.
A first-pass effect is defined as a low systemic availability of the drug as a result of significant metabolism. Although a first-pass effect can occur in a variety of tissues, including the intestines Doherty and Pang (1997) and uterus De Ziegler et al (1997), it is most often observed with the liver.
first-pass metabolism the intestinal and hepatic degradation or alteration of a drug or substance taken by mouth, after absorption, removing some of the active substance from the blood before it enters the general circulation. Synonym(s): first-pass effect first-pass me·tab·o·lism , first-pass effect (fĭrst-pas mĕ-tab'ŏ-lizm, e-fekt') The ...
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.
Drugs.com defines first-pass metabolism as the intestinal and hepatic degradation or alteration of a drug or substance taken by mouth after absorption that removes some of the active substance from the blood before the substance enters the general circulation.
Because the liver is the primary organ of metabolism, the consequence of first-pass metabolism is the break down of significant amounts of a drug before it can reach the systemic circulation, so those drugs never reach the site of action!
Understanding First Pass Metabolism : Drug Absorption. The drug is absorbed from the GI tract and passes via the portal vein into the liver where some drugs are metabolised. Sometimes the result of first pass metabolism means that only a proportion of the drug reaches the circulation. First pass metabolism can occur in the gut and the liver.
First-pass elimination takes place when a drug is metabolised between its site of administration and the site of sampling for measurement of drug concentration. Clinically, first-pass metabolism is important when the fraction of the dose administered that escapes metabolism is small and variable.
The First Pass Effect. When you take a medication by mouth, it doesn't just magically get into your body and start doing its thing. It actually has to go through a whole host of organs and a big ...
Can someone provide a simple explanation for the 1st pass effect? ... First-pass metabolism refers to the 'first passage' of drug through the liver, after absorption from the GI tract, as ...