Phenoxybenzamine (marketed under the trade names Dibenzyline and Dibenyline) is a non-selective, irreversible alpha blocker. Uses
It is 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, although it is currently seldom used for that indication due to unfavourable side effects. It has been used in the treatment of hypoplastic left heart syndrome.It is also used in complex regional pain syndrome (CRPS) type 1 due to its antiadrenergic effects. It has shown to be beneficial if used in the first 3 months of the CRPS diagnosis. Investigational
Phenoxybenzamine has long been known to block ejaculation without affecting semen quality or ability to achieve orgasm, which could make it an effective male contraceptive. This effect is completely reversible, and is believed to be the result of alpha-1 adrenoceptor blockade in the longitudinal muscles of the vas deferens. A dose of 20 mg/day results in aspermia due to reversible paralyzing effects on the vas deferens, ampulla, and ejaculatory ducts. Due to these actions, phenoxybenzamine is also useful for the treatment of premature ejaculation in men. Pharmacology
Phenoxybenzamine is used as an anti-hypertensive due to its efficacy in reducing the vasoconstriction caused by epinephrine (adrenaline) and norepinephrine. Phenoxybenzamine forms a permanent covalent bond with adrenergic receptors.
The main limiting side-effects of alpha antagonists is that the baroreceptor reflex is disrupted and thus this can cause postural hypotension. Phenoxybenzamine also has irreversible antagonist/weak partial agonist properties at the serotonin 5-HT2A receptor. Due to its 5-HT2A receptor antagonism, phenoxybenzamine is useful in the treatment of carcinoid tumor, a neoplasm that secretes large amounts of serotonin and causes diarrhea, bronchoconstriction, and flushing. Stereoisomerism
Phenoxybenzamine contains a stereocenter, so there are two enantiomers, the (R)- and the (S)-forms. All commercial preparations contain the drug as racemate. See also
Ketanserin
Pindobind
Phentolamine

References
External links
 Media related to Phenoxybenzamine at Wikimedia Commons