Phentolamine is a reversible drug with action at both α receptors, which is used to treat hypertensive emergencies and in cases of pheochromocytoma.
Phentolamine is reversible and dissociates from adrenergic receptors.
This drug is reversible, and thus is indicated making it ideal for the diagnosis of a pheochromocytoma.
Phentolamine is indicated for patients on MAO inhibitors who eat tyramine-containing food, in order to treat hypertensive crisis. This drug also has use in cocaine-induced hypertension, as this drug is helpful in avoiding the unopposed alpha effects of other drugs that may be used to treat cocaine intoxication.
Phenoxybenzamine is a non-selective α blocker which is non-reversible. It is often used to treat pheochromocytomas and has a slower onset and longer effect than other α blockers.
Phenoxybenzamine is indicated for the treatment of symptoms from pheochromocytomas, which effect the adrenal gland, as this is drug has a longer effect than other α blockers.
As these medications inhibit α1 and α2 adrenergic receptors, they decrease vasoconstriction and vessel tone. This leads to orthostatic hypotension in patients taking these drugs.
Patients taking this medication may experience reflex tachycardia. This occurs because the hypotension and added α2 inhibition are countered physiologically by increased sympathetic tone.
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