Nebivolol 300 mg (5 mg / 60 capsules)

Most β-blockers are Gα antagonists — they block Gsα-coupled cAMP signalling at β-ARs without activating alternative pathways.

Nebivolol is also a GRK2/β-arrestin biased agonist at β2-AR: it activates GRK2-mediated receptor phosphorylation and β-arrestin recruitment without activating Gsα. β-arrestin then scaffolds EGFR transactivation and ERK1/2 phosphorylation cascades that activate eNOS and promote NO production.

This G protein-independent, β-arrestin-dependent signalling produces vasodilation that is absent from pure Gα-antagonist β-blockers. This biased agonism mechanism is also documented for carvedilol and represents an active area of β-AR pharmacology research.

Direct NO donors (nitroprusside, SNAP, DETA-NONOate) deliver exogenous NO or spontaneously release it, bypassing eNOS entirely. Nebivolol activates endogenous eNOS via β-arrestin/EGFR/Akt signalling, producing NO through the physiological L-arginine/NOS pathway in vascular endothelial cells.

This eNOS-dependent NO production is subject to normal substrate availability, NOS regulation, and shear stress modulation — making nebivolol relevant to studies examining endogenous NO pathway activation versus exogenous NO supplementation. The eNOS pathway activation also produces BH4-dependent effects on NOS coupling that differ from uncoupled exogenous NO delivery.

Nebivolol is predominantly metabolised by CYP2D6 via hydroxylation and glucuronidation. CYP2D6 poor metabolisers (approximately 7–10% of Caucasian populations, 2% of Asians) have significantly higher nebivolol plasma exposure and longer effective half-life compared to extensive metabolisers.

In pharmacogenomic research designs, CYP2D6 genotyping of experimental subjects is important for interpreting interindividual variation in nebivolol PK/PD relationships. This CYP2D6 dependence is shared by several β-blockers (metoprolol, carvedilol) but not others (atenolol, bisoprolol), making nebivolol useful in comparative CYP2D6-dependent versus independent β-blocker metabolism studies.