Alpha 1 Antagonists

First-line drug treatment for male lower urinary tract symptoms

Treatment of primary hypertension (not as first-line therapy)

Preop treatment of pheochromocytoma

Emerging role in treatment of autonomic dysreflexia

Occasionally used in treatment of Raynaud phenomenon

Less commonly used in congenital heart surgery to reduce SVR and correct systemic-to-pulmonary blood flow ratio

Less commonly used to achieve controlled hypotension intraop

Being explored as a potential treatment of posttraumatic stress disorder

Intraop hypotension with attenuated response to the effect of alpha ₁ -agonist therapy

Intraop floppy iris syndrome: Inhibition of iris dilator muscle contraction and tendency of iris to protrude through surgical incision

Orthostatic hypotension, syncope (less with α _1A -selective blockers; more when combined with antihypertensive medication

Reflex tachycardia (less with selective alpha ₁ blockers)

Volume expansion of interstitium and plasma (secondary hyperaldosteronism)

Priapism, urinary incontinence

Other adverse events: Asthenia, nasal congestion, headache, dizziness

Also known as α ₁ -adrenoceptor antagonists (α ₁ -blockers)

Mechanism of action: reversible competitive antagonism of postsynaptic alpha ₁ -adrenergic receptors

Primarily active in tissues that sustain high levels of alpha-adrenergic sympathetic tone (resistance arteries, capacitance veins, urinary bladder outflow tract)

Effect proportional to baseline sympathetic tone

Nonselective (alpha ₁ and alpha ₂ ) adrenergic blockers: Phenoxybenzamine (irreversible) and phentolamine

Selective alpha ₁ -adrenergic blockers: Prazosin (highest affinity), doxazosin, terazosin, silodosin, tamsulosin, bunazosin, alfuzosin

Mixed alpha ₁ and beta-adrenergic blocker: Labetalol

Mixed alpha ₁ -adrenergic and 5-HT1A blocker: Urapidil