Phentolamine
Pronouncation: (fen-TOLE-uh-meen)Class: Agent for pheochromocytoma
Trade Names:
Phentolamine Mesylate
- Powder for Injection 5 mg (as mesylate)/vial
Pharmacology
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Decreases total peripheral resistance and venous return to heart by competitive blockade of presynaptic and postsynaptic alpha-adrenergic receptors.
Pharmacokinetics
Absorption
Not determined.
Distribution
Not determined.
Metabolism
Not determined.
Elimination
Urine (13% as unchanged drug). T 1/2 is 19 min (IV).
Indications and Usage
Prevention or control of hypertensive episodes in patients with pheochromocytoma; pharmacologic test for pheochromocytoma (not method of choice); prevention and treatment of dermal necrosis and sloughing following IV administration or extravasation of norepinephrine or dopamine.
Unlabeled Uses
Control of hypertensive crises secondary to MAOI-sympathomimetic amine interactions or withdrawal of clonidine, propranolol or other antihypertensives; in conjunction with papaverine as intracavernous injection for impotence.
Contraindications
Hypersensitivity to phentolamine or related compounds; MI, coronary insufficiency, angina, or other evidence suggestive of coronary artery disease.
Dosage and Administration
Hypertensive Episodes in PheochromocytomaAdults
IM / IV 5 mg 1 to 2 h before surgery. Repeat if necessary. During surgery, IV 5 mg as indicated.
ChildrenIM / IV 1 mg 1 to 2 h before surgery. During surgery, IV 1 mg as indicated.
Prevention of Dermal Necrosis and SloughingAdults
IV Add 10 mg/1 L of solution containing norepinephrine.
Treatment of Dermal Necrosis or Sloughing After Norepinephrine ExtravasationAdults
5 to 10 mg in 10 mL saline solution in area of extravasation within 12 h.
ChildrenInfiltrate area 0.1 to 0.2 mg/kg (max, 10 mg).
Diagnosis of PheochromocytomaAdults
IM / IV 2.5 to 5 mg.
ChildrenIV 1 mg or IM 3 mg.
General Advice
- Dilute 5 mg in 1 mL Sterile Water for Injection. May dilute further with 5 to 10 mL Sterile Water for Injection.
- Use reconstituted solution immediately; do not store.
Storage/Stability
Store unopened vials at controlled room temperature (59° to 86°F).
Drug Interactions
Epinephrine, ephedrineVasoconstrictive and hypertensive effects of epinephrine and ephedrine are antagonized by phentolamine.
Laboratory Test Interactions
None well documented.
Adverse Reactions
Cardiovascular
Acute and prolonged hypotensive episodes; tachycardia; cardiac arrhythmias; orthostatic hypotension.
CNS
Weakness; dizziness.
EENT
Nasal stuffiness.
GI
Nausea; vomiting; diarrhea.
Miscellaneous
Flushing.
Precautions
Pregnancy
Category C .
Lactation
Undetermined.
CV effects
Marked hypotensive episodes and shocklike states may follow use of phentolamine and lead to MI, cerebrovascular spasm, or cerebrovascular occlusion.
Screening tests
Urinary assays of catecholamines or other biochemical assays have largely supplanted phentolamine and other pharmacologic tests for pheochromocytoma. Phentolamine is usually used as confirmation. Follow specific guidelines for use of phentolamine.
Overdosage
Symptoms
Severe hypotension, shock, tachycardia, flushing.
Patient Information
- Instruct patient to avoid sudden position changes to prevent orthostatic hypotension.
- Instruct patient to notify health care provider if chest pain develops during infusion.
- Tell patient to report the following symptoms to health care provider: dizziness, fainting spells or weakness.
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More Phentolamine resources:
Phentolamine Intracavernosal - Includes detailed dosage instructions.
Phentolamine Drug Interactions
Pheochromocytoma Diagnosis, Pheochromocytoma, Dermal Necrosis -- Treatment











