Alpha blocker

Alpha blockers, also known as α-blockers or α-adrenoreceptor antagonists, are a class of pharmacological agents that act as antagonists on α-adrenergic receptors (α-adrenoceptors).

Historically, alpha-blockers were used as a tool for pharmacologic research to develop a greater understanding of the autonomic nervous system. Using alpha blockers, scientists began characterizing arterial blood pressure and central vasomotor control in the autonomic nervous system. Today, they can be used as clinical treatments for a limited number of diseases.

Alpha blockers can treat a small range of diseases such as hypertension, Raynaud's disease, benign prostatic hyperplasia (BPH) and erectile dysfunction. Generally speaking, these treatments function by binding an α-blocker to α receptors in the arteries and smooth muscle. Ultimately, depending on the type of alpha receptor, this relaxes the smooth muscle or blood vessels, which increases fluid flow in these entities.

Classification

α1-blockers act on α1-adrenoceptors

α2-blockers act on α2-adrenoceptors

When the term "alpha blocker" is used without further qualification, it can refer to an α1 blocker, an α2 blocker, a nonselective blocker (both α1 and α2 activity), or an α blocker with some β activity. However, the most common type of alpha blocker is α1.

Non-selective α-adrenergic receptor antagonists include:

Phenoxybenzamine

Phentolamine

Tolazoline

Trazodone

Selective α1-adrenergic receptor antagonists include:

Alfuzosin

Doxazosin

Prazosin (inverse agonist)

Tamsulosin

Terazosin

Silodosin

Selective α2-adrenergic receptor antagonists include:

Atipamezole

Idazoxan

Mirtazapine

Yohimbine

Finally, the agents carvedilol and labetalol are both α and β-blockers.