first-pass metabolism


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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 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.

first-pass metabolism

The metabolism of a substance that occurs immediately as it enters the body, and before it can exert any effect, or before it can be measured at its target organ.
See also: metabolism
References in periodicals archive ?
Utility of in vitro systems and preclinical data for the prediction of human intestinal first-pass metabolism during drug discovery and preclinical development.
Similar to pMDIs, a nasal spray offers similar dose size limitations, rapid onset, and bypasses the first-pass metabolism.
Site and quantitative importance of alcohol first-pass metabolism.
The main impact of liver disease is on phase I enzymes, which will affect both clearance and first-pass metabolism.
Therefore the Sprague-Dawley rat liver microsomes may be useful for assessing herb-drug interaction in the hepatic first-pass metabolism responsible for CYP1A2 at the early drug-discovery stage because of similar typical substrates and metabolism activities as humans.
5 h] after high-dose Sativex were facilitated THC absorption through the oral mucosa and reduced first-pass metabolism.
Avoiding first-pass metabolism in the liver prevents production of metabolites that can alter a drug's safety and side effect profile, said Dr.
Unfortunately, a major drawback of Invirase was its limited bioavailability due to incomplete absorption and extensive first-pass metabolism.
It has recently been reported that alcohol dehydrogenase (ADH) activity in gastric mucosa contributes substantially to the first-pass metabolism of ethanol[5], and that activities in the stomach are lower in women than in men[6].
Lieber notes that studies of males reported by his team in the February 1989 GASTROENTEROLOGY indicate that some drugs -- including cimetidine, widely presribed to control gastric ulcers -- can inhibit the stomach's first-pass metabolism of alcohol.
This approach considers separately the various mechanisms involved in drug absorption, such as transit time, gut wall permeability, gut wall metabolism, and hepatic first-pass metabolism from dissolution rate.