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First Pass Metabolism

First pass metabolism can occur in the gut wall, portal vein (uncommon) and in the liver.

Note that high rates of metabolism at either site result in low oral availability.

Use the sliders to see how alteration of gut wall metabolism and hepatic metabolism contribute to first pass metabolism and hence oral availability.

Main Arrows
Main Arrows
Main Arrows




Systemic Blood Stream (Vena Cava)

Portal Vein

Gut Wall

Oral Availability

Low High
Low High