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Alpha-1 blockers (also called alpha-adrenergic blocking agents or alpha-1 antagonists) constitute a variety of drugs that block the effect of catecholamines on alpha-1-adrenergic receptors. They are mainly used to treat benign prostatic hyperplasia (BPH), hypertension and post-traumatic stress disorder. Alpha-1 adrenergic receptors are present in vascular smooth muscle, the central nervous system, and other tissues. When alpha blockers bind to these receptors in vascular smooth muscle, they cause vasodilation.
Over the last 40 years, a variety of drugs have been developed from non-selective alpha-1 antagonists to selective alpha-1 antagonists and alpha-1 inverse agonists. The first drug that was used was a non-selective alpha blocker, named phenoxybenzamine and was used to treat BPH. Currently, several relatively selective alpha-1 antagonists are available. As of 2018, prazosin is the only alpha-1 blocker known to act as an inverse agonist at all alpha-1 adrenergic receptor subtypes; whereas tamsulosin is a selective antagonist for all alpha-1 subtypes. Drugs that act as selective antagonists at specific alpha-1 adrenergic receptor subtypes have also been developed.

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