| Item |
Information |
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Drug Groups
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approved |
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Description
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An alpha-adrenergic antagonist with long duration of action. It has been used to treat hypertension and as a peripheral vasodilator. [PubChem] |
| Indication |
For the treatment of phaeochromocytoma (malignant), benign prostatic hypertrophy and malignant essential hypertension. |
| Pharmacology |
Phenoxybenzamine is indicated for the control of episodes of hypertension and sweating that occur with a disease called pheochromocytoma. If tachycardia is excessive, it may be necessary to use a beta-blocking agent concomitantly. Phenoxybenzamine is a long-acting, adrenergic, alpha-receptor blocking agent which can produce and maintain "chemical sympathectomy" by oral administration. It increases blood flow to the skin, mucosa and abdominal viscera, and lowers both supine and erect blood pressures. It has no effect on the parasympathetic system. Phenoxybenzamine works by blocking alpha receptors in certain parts of the body. Alpha receptors are present in the muscle that lines the walls of blood vessels. When the receptors are blocked by Phenoxybenzamine, the muscle relaxes and the blood vessels widen. This widening of the blood vessels results in a lowering of blood pressure. |
| Toxicity |
Symptoms of overdose are largely the result of block of the sympathetic nervous system and of the circulating epinephrine. They may include postural hypotension resulting in dizziness or fainting, tachycardia, particularly postural, vomiting; lethargy, and shock. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Absorption |
Twenty to 30 percent of orally administered phenoxybenzamine appears to be absorbed in the active form. |
| Half Life |
24 hours |
| References |
| • |
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.
[Pubmed]
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| • |
Frang H, Cockcroft V, Karskela T, Scheinin M, Marjamaki A: Phenoxybenzamine binding reveals the helical orientation of the third transmembrane domain of adrenergic receptors. J Biol Chem. 2001 Aug 17;276(33):31279-84. Epub 2001 Jun 6.
[Pubmed]
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