The first-pass effect of pregabalin in the liver?

Short answer: negligible.

Details:
- Pregabalin undergoes essentially no hepatic metabolism. It is not a substrate of cytochrome P450 enzymes.
- It is absorbed with high oral bioavailability (about 90%), and most of the drug is excreted unchanged in the urine.
- Because there is minimal hepatic metabolism, the hepatic first-pass effect is negligible. The drug’s clearance is mainly renal.
- Clinical implication: hepatic impairment generally does not require dose adjustment for pregabalin. Dosing adjustments are mainly needed for renal impairment, not liver disease.