Phenoxybenzamine

• (RS )-N- benzyl-N- (2-chloroethyl ) -1 - ( phenoxy) - -2-aminopropane (IUPAC)
• (RS) -benzyl -(2- chloroethyl) - ( β - phenoxyisopropyl )-amine
• Dibenylin

C04AX02, G04BD20

Alpha blockers

38-40 ° C

Hydrochloride

Attention

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Phenoxybenzamine is a drug that belongs to the group of alpha-blocker ( α - sympatholytic ). He has a peripheral blood vasodilator and is used as an antihypertensive in pheochromocytoma.

In Germany phenoxybenzamine is also used as an antispasmodic urological neurogenic bladder dysfunction application.

The active ingredient is used in racemic form.

Mechanism of Action

Phenoxybenzamine is an irreversible blocker of α1 - and α2 - receptors, the blockade is based on an alkylation of the receptor.

Adverse effects

The most serious side effect of phenoxybenzamine is orthostatic hypotension, which is characteristic of an alpha-blocker.

Production

The synthesis of racemic phenoxybenzamine possible gradually from 1- phenoxypropan -2-ol. First, the alcohol function is substituted by a chlorine atom by means of thionyl chloride, then a nucleophilic substitution with ethanolamine. The secondary amine thus obtained is reacted with benzyl chloride and then reacted with the introduced ethanolamine alcohol function analogously to the first step of thionyl chloride to give the chloro derivative. This is first obtained as the hydrochloride from which the free base is liberated using sodium hydroxide solution. The required starting material 1- Phenoxypropan -2 -ol is accessible from the major industrial products of propylene oxide and phenol.

Stereoisomerism

Phenoxybenzamine contains a stereogenic center, so there are two enantiomers, the ( R) form and the ( S) form. All commercial preparations containing the drug as a racemate.

Trade names

Phenoxybenzamine in Germany and Austria under the name Dibenzyran commercially available.