Glossary

First-Pass Metabolism

Pharmacology

First-Pass Metabolism — The rapid metabolism of an orally administered compound by the liver before it reaches systemic circulation, a major barrier for oral peptide delivery.

What Is First-Pass Metabolism?

First-pass metabolism is the degradation of an orally administered peptide in the GI tract and liver before reaching systemic circulation. First-pass metabolism reduces oral bioavailability to near zero for most peptides due to gastric acid, luminal proteases (pepsin, trypsin), and hepatic enzymes.

Overcoming First-Pass

Enteric coating: Protect peptide from gastric acid and pepsin until intestinal release
Permeation enhancers: SNAC (semaglutide), sodium caprate increase intestinal absorption
Protease inhibitors: Co-formulated aprotinin or soybean trypsin inhibitor reduce luminal degradation
Alternative routes: SC, intranasal, sublingual bypass GI and hepatic first-pass

Frequently Asked Questions

What is First-Pass Metabolism?

The rapid metabolism of an orally administered compound by the liver before it reaches systemic circulation, a major barrier for oral peptide delivery.

Why is First-Pass Metabolism important in peptide research?

First-Pass Metabolism is a fundamental concept in pharmacology as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.

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