Non-Selective Alpha Blockers

Non-selective alpha blockers inhibit both α1 and α2 receptors, which results in postural hypotension from blockade of α2 receptors.  These drugs are used primarily in treatment of pheochromocytoma, which is a tumor of the adrenal gland that secretes catecholamines.  Phentolamine competitively blocks α1 and α2 receptors and is used for short-term treatment of pheochromocytoma. Phenoxybenzamine covalently binds α1 and α2 receptors and is used in long-term treatment of inoperable pheochromocytoma or prior to surgery for removal. To overcome the effects of phenoxybenzamine, the body must produce additional α1 and α2 receptors.   

Class Drugs

• Phenoxybenzamine

• Phentolamine

Class Mechanism of Action

• Blocks alpha-1 and alpha-2 receptors

Class Application

• See Below

Class Adverse Effects

• See Below

Drug Table

Drug Name	Application	Comments	Image
Phenoxybenzamine	Reversal of Epinephrine; Treatment of Pheochromocytoma	Covalently binds alpha-1 and alpha-2 receptors:; -Synthesis of new receptors is only way to overcome blockade; -Reverses alpha action of epinephrine (epinephrine causes hypotension in setting of phenoxybenzamine); Adverse Effects:; -Postural hypotension; -Tachycardia; -NauseaVomiting; -Inhibition of ejaculation	"Fence" and "Ox" and "Mercedes-Benz symbol"
Phentolamine	Short-term management of pheochromocytoma; Local treatment of extravasation of norepinephrine; Treatment of clonidine withdrawal (hypertension)	Competitively blocks alpha-1 and alpha-2 receptors:; - Reverses alpha action of epinephrine (epinephrine causes hypotension in setting of phentolamine); Adverse Effects:; -Postural hypotension; -Arrhythmia; -Anginal pain; -Contraindicated in patients with coronary artery disease	"Fence" and "Toe"