Dangerous Drug: Phentolamine Mesylate(fen tole’ a meen)
OraVerse, Rogitine (CAN)
PREGNANCY CATEGORY C
Drug Classes
Alpha-adrenergic blocker
Diagnostic agent
Therapeutic Actions
Competitively blocks postsynaptic alpha1-adrenergic receptors, decreasing sympathetic tone on the vasculature, dilating blood vessels, and lowering arterial BP (no longer used to treat essential hypertension because it also blocks presynaptic alpha2-adrenergic receptors that are believed to mediate a feedback inhibition of further norepinephrine release; this accentuates the reflex tachycardia caused by the lowering of BP); use of phentolamine injection as a test for pheochromocytoma depends on the premise that a greater BP reduction will occur with pheochromocytoma than with other etiologies of hypertension.
Indications
Pheochromocytoma: Prevention or control of hypertensive episodes that may result from stress or manipulation during preoperative preparation and surgical excision
Pharmacologic test for pheochromocytoma (urinary assays of catecholamines, other biochemical tests have largely supplanted the phentolamine test)
Prevention and treatment of dermal necrosis and sloughing following IV administration or extravasation of norepinephrine or dopamine
Reversal of soft-tissue anesthesia (OraVerse)
Unlabeled use: Treatment of hypertensive crises secondary to interactions between MAOIs and sympathomimetic amines, or secondary to rebound hypertension on withdrawal of clonidine, propranolol, or other antihypertensives
Contraindications and Cautions
Contraindicated with hypersensitivity to phentolamine or related drugs, evidence of CAD (MI, angina, coronary insufficiency).
Use cautiously with pregnancy, lactation.
Available Forms
Injection—0.4 mg/1.7 mL, 5 mg/mL
Dosages
Adults
Prevention or control of hypertensive episodes in pheochromocytoma: For use in preoperative reduction of elevated BP, inject 5 mg IV or IM 1–2 hr before surgery. Repeat if necessary. Administer 5 mg IV during surgery as indicated to control paroxysms of hypertension, tachycardia, respiratory depression, seizures, or other effects of epinephrine toxicity.
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