Phenoxybenzamine
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Phenoxybenzamine
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| Systematic (IUPAC) name | |
| N-benzyl-N-(2-chloroethyl)-1-phenoxy-propan-2-amine | |
| Identifiers | |
| CAS number | |
| ATC code | C04 |
| PubChem | |
| DrugBank | |
| Chemical data | |
| Formula | C18H22ClNO |
| Mol. mass | 303.826 g/mol |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Metabolism | ? |
| Half life | 24 hours |
| Excretion | ? |
| Therapeutic considerations | |
| Pregnancy cat. |
? |
| Legal status | |
| Routes | ? |
Phenoxybenzamine is a non-specific, irreversible alpha blocker used in the treatment of hypertension, and specifically that caused by pheochromocytoma. It has a slower onset and a longer lasting effect compared with other alpha blockers. It was also the first alpha blocker to be used for treatment of benign prostatic hyperplasia,[1] although it is currently seldom used for that indication due to an unfavourable side effects profile.
[edit] Pharmacology
Phenoxybenzamine is used as an anti-hypertensive due to its efficacy in reducing the vasoconstriction caused by noradrenaline. Phenoxybenzamine forms a permanent covalent bond with nitrogen atoms on the surface of the alpha adrenoceptors, blocking adrenaline and noradrenaline from binding with the receptor. This causes vasodilatation in blood vessels, due to its antagonistic effect on the alpha-1 adrenoceptor found in the walls of blood vessels, resulting in a drop in blood pressure.
It will also affect the alpha 1 and 2 receptors found in the nervous system, where this will reduce sympathetic activity. This is due to its effect on the postsynaptic membrane adrenoceptors in the second synapse of the sympathetic nervous pathway, and will therefore reduce the 'fight or flight' output of the sympathetic nervous system. This results in further general vasodilation, pupil constriction, an increase in GI tract motility and secretions, and glycogen synthesis.
[edit] References
Day, M.D. (1979). Autonomic Pharmacology Experimental and Clinical Aspects. Churchill Livingstone.
Bullock, S. Galbraith, A. Hunt, B. Manias, E. and Richards, A. (1999). Fundamentals of Pharmacology. Pearson Education Limited publishing as Prentice Hall.
- ^ Caine M, Perlberg S, Meretyk S.A placebo-controlled double-blind study of the effect of phenoxybenzamine in benign prostatic obstruction. Br J Urol. 1978 Dec;50(7):551-4. PMID 88984
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