- Phenoxybenzamine is a long-acting, non-selective, and irreversible alpha-adrenergic receptor antagonist.
- It is primarily used to manage hypertension and sweating associated with pheochromocytoma, a rare tumor of the adrenal glands that produces excess catecholamines (like adrenaline).
Chemical Structure & Formula:
- Features a phenoxy group attached to an aliphatic chain terminating in an amine, capable of covalent (irreversible) receptor binding.
- Approximate Formula: C₂₁H₂₇NO
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Mechanism of Action:
- Irreversibly blocks both α₁ and α₂ receptors through alkylation of nucleophilic sites on the receptor proteins.
- This results in a long-lasting blockade and sustained vasodilation.
Side Effects of Phenoxybenzamine:
- Orthostatic hypotension
- Reflex tachycardia
- Nasal congestion
- Gastrointestinal disturbances
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Clinical Uses of Phenoxybenzamine:
- Primarily used preoperatively in patients with pheochromocytoma to prevent catecholamine-induced hypertensive episodes.
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