Phenoxybenzamine

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Phenoxybenzamine
Systematic (IUPAC) name
N-benzyl-N-(2-chloroethyl)-1-phenoxy-propan-2-amine
Identifiers
CAS number	59-96-1
ATC code	C04AX02
PubChem	4768
DrugBank	APRD00651
Chemical data
Formula	C18H22ClNO
Mol. weight	303.826 g/mol
Pharmacokinetic data
Bioavailability	?
Metabolism	?
Half life	24 hours
Excretion	?
Therapeutic considerations
Pregnancy cat.	?
Legal status
Routes	?

Phenoxybenzamine is an irreversible alpha blocker used in the treatment of hypertension. 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] Pharmocology

Phenoxybenzamine is used as an anti-hypertensive due to its efficacy in reducing the vasoconstriction caused by norepinephrine. Drugs such as phenoxybenzamine block the α1 adrenoreceptors on the postsynaptic membrane and thus prevent the noradrenaline from bonding with the α1 adrenoreceptors. The effect of this is that the sympathetic nervous system is inhibited leading to a greater effect from the parasympathetic. This results in vasodilation, pupil constriction, an increase in GI tract motility and secretions, glycogen synthesis and impotence. Such responses inhibit the “fight or flight” mechanism.

[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.

1. ^ 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