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Phenoxybenzamine chemical structure
|ATC code |
|Molecular weight||303.826 g/mol|
|Elimination half-life||24 hours|
|Pregnancy category||C (U.S.)|
|Routes of administration||Oral|
Phenoxybenzamine (marketed under the trade name Dibenzyline) is a non-specific, irreversible alpha blocker.
Uses[edit | edit source]
It is also used in Complex Regional Pain Syndrome Type 1 due to it's anti-adrenergic affects. It has shown to be beneficial if used in the first 3 months of CRPS diagnosis.
Pharmacology[edit | edit source]
Phenoxybenzamine is used as an anti-hypertensive due to its efficacy in reducing the vasoconstriction caused by adrenaline and noradrenaline. Phenoxybenzamine forms a permanent covalent bond with adrenergic receptors. Based on what we know about the structures of these receptors, it likely involves attack by the cysteine at position 3.36 in transmembrane helix 3 to form a stable linkage. Thus, it remains permanently bound to the receptor, preventing adrenaline and noradrenaline from binding. This causes vasodilatation in blood vessels, due to its antagonistic effect at the alpha-1 adrenoceptor found in the walls of blood vessels, resulting in a drop in blood pressure.
It will also affect the postsynaptic alpha 1 and 2 receptors in the nervous system, and so reduce sympathetic activity. This results in further vasodilation, pupil constriction, an increase in GI tract motility and secretions, and glycogen synthesis.
References[edit | edit source]
- Caine M, Perlberg S, Meretyk S (1978). A placebo-controlled double-blind study of the effect of phenoxybenzamine in benign prostatic obstruction. British journal of urology 50 (7): 551–4.
- Guzzetta NA (August 2007). Phenoxybenzamine in the treatment of hypoplastic left heart syndrome: a core review. Anesth. Analg. 105 (2): 312–5.
- Frang H, Cockcroft V, Karskela T, Scheinin M, Marjamäki A (2001). Phenoxybenzamine binding reveals the helical orientation of the third transmembrane domain of adrenergic receptors. J. Biol. Chem. 276 (33): 31279–84.
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