Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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3-[N-(2-imidazolin-2-ylmethyl)-4-methylanilino]phenol; CAS number 50-60-2; CAS number: 73-05-2; Phentolamine monohydrochloride

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Phentolamine is a non-selective alpha-receptor antagonist. The drug has the molecular formula C17H19N3O and a molar mass of 281.35 g-mol-1. It blocks both α1 and α2 adrenoreceptors for a relatively short period of time and thus the effect of the neurotransmitters adrenaline and noradrenaline (Hersh EV et al. 2019). Phentolamine lowers blood pressure, increases heart rate. The substance also reduces venous tone.

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Phentolamine is used parenterally to treat hypertension crises such as pheochromocytoma.

Antidote: The drug is used as an antidote for intoxications caused by indirect sympathomimetics such as cocaine, amphetamine and amphetamine-like substances.

Pheochromocytoma: The drug is used in the treatment of hypertension crises in pheochromocytoma, also during preoperative preparation and surgical intervention. Dosage: In intensive care medicine it is used in adults with a dosage of 50 to 500 µg/min.

Phentolamine inhibition test: Another field of application is a diagnostic test procedure (phentolamine inhibition test).

Erectile dysfunction: Erectile dysfunction (Dinsmore WW et al. 2008): Phentolamine is suitable in combination with papaverine for self-injection into the erectile tissue. Intracavernous therapy often causes priapism. In this respect, patients must be familiarised with the method in several rounds carefully and without time pressure - possibly by specially trained nursing staff.

Dentistry: Phentolamine mesilate allows the anaesthetic to flow off by dilating the blood vessels and thus increasing the blood flow rate (cancelling the epinephrine effect). In clinical trials, the drug reduced the time to regain lip sensation to 75 to 85 minutes, more than half of the time needed to regain lip sensation.

Undesirable effects
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The most common side effects of phentolamine are headache, agitation and tachycardia in response to the drop in blood pressure (reflex tachycardia), bradycardia and pain at the injection site.

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  1. Dinsmore WW et al (2008) Vasoactive intestinal polypeptide/phentolamine for intracavernosal injection in erectile dysfunction. BJU Int 102:933-937.
  2. Gould L et al (1976) Phentolamines. On Heart J 92:397-402.
  3. Hersh EV et al (2019) Phentolamine mesylate: pharmacology, efficacy, and safety. Gene Dent. 67:12-17.


Last updated on: 29.10.2020