A new drug administered orally shows significantly lower plasma concentrations than expected despite complete absorption from the gut. Which process explains why this 'first-pass' effect dominates the bioavailability?

💡 Explanation

The first-pass effect describes extensive drug metabolism in the liver before systemic circulation. This leads to lower bioavailability because the liver metabolizes a significant fraction of the drug before it reaches its target, therefore, hepatic metabolism causes reduced plasma concentrations, rather than renal excretion or protein binding.

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