How nebivolol produces vasodilatation even it is a beta blocker?

Nebivolol, as the suffix ‘olol’  indicates, belongs to the category of beta blockers. It has additional vasodialtory action due to release of nitric oxide.

β₁ receptors are present on the heart whereas β₂ receptors are present on smooth muscles including vascular smooth muscle.

When β₁ receptors are activated they increase both rate and force of contraction of the heart. Hence they increase cardiac output as well as cardiac work.

Similarly β₂ receptors are responsible for smooth muscle relaxation such as bronchodilation and vasodilation. But vasodilation is observed mainly at skeletal and hepatic blood vessels where β₂ receptors are abundant. On the other hand majority of systemic blood vessels are predominant with α₁ receptors.

So non-selective beta blockers like propranolol blocks both β₁ and β₂ receptors resulting in cardiac inhibition and inhibition of bronchodilation. But they don’t have any direct effect on major blood vessels as the later are expressed with α₁ receptors.

Similarly selective β₁ blockers mainly act on heart decrease both rate and force of contraction. They decrease cardiac output thereby cardiac work and blood pressure. Again these drugs don’t have any direct effect on blood vessels.

Nebivolol is an exceptional drug. It acts both on β₁ receptors as well as blood vessels. It acts on β₁ receptors thereby decrease force and rate of contraction hence cardiac work.

On the other hand it acts on vascular endothelium and releases nitric oxide which causes vasodilation. As the blood vessels are dilated, it decreases both afterload and preload thereby decreases cardiac work.

It also improves blood supply by vasodilation. Hence it is preferred in hypertension associated with angina.