Prodrugs and first-pass metabolism

Learning objective

Distinguish metabolic activation from loss before systemic circulation.

When transformation produces activity

The lecture uses prodrugs to show that metabolism can generate an active compound rather than simply end an effect. The parent and product can have different time courses. A change in metabolism may therefore change both disappearance of the parent and formation of the active product.

Before systemic entry

First-pass metabolism occurs before an absorbed dose reaches systemic circulation, notably in the gut wall and liver after oral administration. It can reduce the fraction of unchanged parent reaching systemic blood. Routes differ in their initial path to circulation, but bypassing part of first-pass metabolism does not prevent later metabolism. The lecture's drug-combination and route-switching examples are not reproduced as instructions.

Prodrug

A compound administered so that metabolic conversion produces an active drug.

First-pass metabolism

Metabolism before a dose reaches systemic circulation, often involving the gut wall and liver.

Pharmacology, kinetics and dynamics

Professor deck 04, PDF pages 41, 42, 43. Course material is paraphrased. Qualifications and excluded clinical generalizations are documented in the Pharmacokinetics editorial record. Source review does not establish clinical validation.

Examples and practice explanations are original study aids, not professor quotations, exam requirements or medication instructions.