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Pharmacy & Pharmacology vocabulary · Pharmacokinetics

First-pass metabolism

Meaning in pharmacy & pharmacology, with examples

nounAdvanced term

In pharmacy & pharmacology, first-pass metabolism means: The breakdown of a swallowed drug in the gut wall and liver before it reaches the general circulation, which lowers the amount that can act in the body.

In Turkish: ilk geçiş metabolizması, ilk geçiş etkisi

How it is used

Also called the first-pass effect. Drugs absorbed from the gut travel through the portal vein to the liver first. Drugs with high first-pass metabolism, such as glyceryl trinitrate, are given by other routes (sublingual, IV, patches), or their oral doses are much higher than the IV dose.

Example sentences

  1. Because of extensive first-pass metabolism, the oral dose is much higher than the IV dose.

  2. The sublingual route avoids first-pass metabolism because the drug goes straight into the blood.

Common collocations

  • extensive first-pass metabolism
  • first-pass effect
  • avoid first-pass metabolism
  • hepatic first-pass
  • metabolismThe chemical changes that the body, mainly the liver, makes to a drug, usually turning it into substances that are less active and easier to remove.
  • bioavailabilityThe proportion of a dose that reaches the general circulation unchanged and can act in the body; by definition it is 100 percent for intravenous drugs.
  • sublingualPlaced under the tongue and left to dissolve, so that the drug is absorbed directly into the blood through the lining of the mouth.
  • oralTaken by mouth and swallowed, so that the medicine is absorbed through the digestive system; the most common route for medicines.

More terms: Pharmacokinetics

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