Chemical Properties
Phentolamine mesylate is a white, odourless powder which is soluble in water and alcohol.
Uses
Phentolamine mesilate is an adrenergic blocking agent and antihypertensive. It is used in the treatment of hypertension and hypertensive emergencies, pheochromocytoma, vasospasm of raynaud disease and frostbite, clonidine withdrawal syndrome, impotence, and peripheral vascular disease.
brand name
Regitine
(Novartis) [Name previously used: Phentolamine Methanesulfonate.].
General Description
Phentolamine Mesylate belongs to the class of alpha adrenergic antagonist drugs. It is used in the treatment of pheochromocytoma-related hypertension, erectile dysfunction and in the diagnosis of pheochromocytoma and norepinephrine-related dermal necrosis.
Biochem/physiol Actions
α-Adrenergic receptor antagonist; peripheral vasodilator.
Clinical Use
Alpha-adrenoceptor blocker:
Hypertensive crisis
Safety Profile
Poison by intravenous and subcutaneous routes. Experimental reproductive effects. When heated to decomposition it emits toxic fumes of SOx and NOx.
Drug interactions
Potentially hazardous interactions with other drugs
Anaesthetics: enhanced hypotensive effect.
Antidepressants: additive hypotensive effect with
MAOIs - avoid.
Antihypertensives: enhanced hypotensive effect.
Avanafil, vardenafil, sildenafil and tadalafil: enhanced
hypotensive effect - avoid concomitant use.
Diuretics: enhanced hypotensive effect.
Linezolid: additive hypotensive effect.
Moxisylyte: possibly severe postural hypotension.
Metabolism
Phentolamine is extensively metabolised.
Only about 10-13% of an intravenous dose is excreted
unchanged in the urine, and the fate of the remainder of
the drug is unknown.
Mode of action
Phentolamine Mesylate is the mesylate salt of a synthetic imidazoline with alpha-adrenergic antagonist activity. As a competitive alpha-adrenergic antagonist, phentolamine binds to alpha-1 and alpha-2 receptors, resulting in a decrease in peripheral vascular resistance and vasodilatation. This agent also may block 5-hydroxytryptamine (5-HT) receptors and stimulate release of histamine from mast cells.
