Phentolamine Mesylate

Pronunciation: fen-TOL-a-meen MES-i-late
Class: Agent for pheochromocytoma

Trade Names

OraVerse
- Injection, solution 0.4 mg per 1.7 mL supplied in a dental cartridge

Phentolamine Mesylate
- Injection, lyophilized powder for solution 5 mg

Pharmacology

Produces an alpha-adrenergic block that results in vasodilatation when applied to vascular smooth muscle and positive inotropic and chronotropic effects on cardiac muscle.

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Pharmacokinetics

Absorption

T _max is 10 to 20 min ( OraVerse ).

Elimination

Urine (13% as unchanged drug). Half-life is 19 min (IV) and 2 to 3 h ( OraVerse ).

Special Populations

OraVerse C _max 3.5-fold higher in children weighing 15 to 30 kg compared with children weighing more than 30 kg. AUC was similar.

Indications and Usage

Prevention or control of hypertensive episodes in patients with pheochromocytoma (excluding OraVerse ); pharmacologic test for pheochromocytoma (not method of choice) (excluding OraVerse ); prevention and treatment of dermal necrosis and sloughing following IV administration or extravasation of norepinephrine (excluding OraVerse ); reversal of soft-tissue anesthesia (ie, anesthesia of lip and tongue) ( OraVerse only).

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, history of MI, coronary insufficiency, angina, or other evidence suggestive of coronary artery disease.

Dosage and Administration

IM / IV 5 mg.

IM/IV 1 mg IV or 3 mg IM.

IM / IV 5 mg 1 to 2 h before surgery. Repeat if necessary. During surgery, IV 5 mg as indicated.

IM / IV 1 mg 1 to 2 h before surgery. Repeat if necessary. During surgery, IV 1 mg as indicated.

IV Add 10 mg/L of solution containing norepinephrine.

5 to 10 mg in 10 mL of saline solution in area of extravasation within 12 h.

Based on the amount of local anesthetic administered. One-half cartridge local anesthetic, 0.2 mg (½ cartridge). One cartridge local anesthetic 0.4 mg (1 cartridge). Two cartridges local anesthetic, 0.8 mg (2 cartridges).

See Adults for dosing; do not exceed 0.4 mg (1 cartridge).

Max dose is 0.2 mg (½ cartridge).

General Advice

• For diagnosis of pheochromocytoma, phentolamine IV is injected rapidly. Record blood pressure immediately after injection, at 30-sec intervals for first 3 min, and at 60-sec intervals for the next 7 min.
• Dilute 5 mg in 1 mL of sterile water for injection for IV or IM administration for diagnosis of pheochromocytoma.
• Use reconstituted solution immediately; do not store.
• OraVerse should be administered using the same location(s) and technique(s) employed for administration of the local anesthetic.
• Withhold sedatives, analgesics, and all other medicines, except those deemed essential (eg, digoxin, insulin), for at least 24 h prior to test for diagnosis of pheochromocytoma.

Storage/Stability

Store unopened vials between 59° and 86°F. Protect OraVerse from direct heat and light. Do not allow to freeze.

Drug Interactions

Withhold prior to test for diagnostic of pheochromocytoma; do not perform this test on normotensive patients.

Vasoconstrictive and hypertensive effects of epinephrine and ephedrine are antagonized by phentolamine.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Tachycardia (6%); bradycardia (4%); acute and prolonged hypotensive episodes, cardiac arrhythmias, orthostatic hypotension (postmarketing).

GI

Oral pain (less than 10%) ( OraVerse ).

Miscellaneous

Postprocedural pain (10%) ( OraVerse ); injection-site pain (6%) ( OraVerse ).

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

OraVerse is not recommended for use in children younger than 6 yr of age or weighing less than 15 kg. Phentolamine injection IM or IV is recommended for children. See Administration and Dosage.

CV effects

Marked hypotensive episodes and shock-like states may follow use of phentolamine and may lead to MI, cerebrovascular spasm, or cerebrovascular occlusion. Tachycardia and cardiac arrythmias may also occur.

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

Diarrhea, excitation, headache, hypoglycemia, nausea, pupillary contraction, severe hypotension, shock, sweating, tachycardia, visual disturbances, vomiting.

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.
• Advise patient to report the following symptoms to health care provider: dizziness, fainting spells, or weakness.

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