Phentolamine mesylate
Phentolamine mesylate (Regitine)
Phentolamine mesylate
(fen- TOLL-ah-meen)
Pregnancy Category: C Regitine Rogitine Vasomax (Rx)

Classification: Alpha-adrenergic blocking agent

Action/Kinetics: Phentolamine competitively blocks both presynaptic (alpha-2) and postsynaptic (alpha-1) adrenergic receptors producing vasodilation and a decrease in peripheral resistance. The drug has little effect on BP. In CHF, phentolamine reduces afterload and pulmonary arterial pressure as well as increases CO. Onset (parenteral): Immediate. Duration: Short. Poorly absorbed from the GI tract. About 10% excreted unchanged in the urine after parenteral use.

Uses: Prophylaxis or treatment of hypertension in pheochromocytoma as a result of stress or manipulation prior to or during surgery. Dermal necrosis and sloughing following IV use or extravasation of norepinephrine or dopamine. To test for pheochromocytoma (not the method of choice). Investigational: Hypertensive crisis secondary to MAO inhibitor/sympathomimetic amine interactions; rebound hypertension due to withdrawal of clonidine, propranolol, or other antihypertensive drugs. In combination with papaverine as an intracavernous injection for impotence.

Contraindications: CAD including angina, MI, or coronary insufficiency.

Special Concerns: Use during pregnancy and lactation only if benefits clearly outweigh risks. Geriatric clients may have a greater risk of developing hypothermia. Use with great caution in the presence of gastritis, ulcers, and clients with a history thereof. Defer use of cardiac glycosides until cardiac rhythm returns to normal.

Side Effects: CV: Acute and prolonged hypotension, tachycardia, MI, cerebrovascular spasm, cerebrovascular occlusion and arrhythmias, especially after parenteral administration. Orthostatic hypotension, flushing. GI: N&V;, diarrhea. Other: Dizziness, weakness, nasal stuffiness.

Overdose Management: Symptoms: Hypotension, shock. Treatment: Maintain BP by giving IV norepinephrine (DO NOT USE EPINEPHRINE).

Drug Interactions: Ephedrine / Vasoconstrictor and hypertensive effect antagonized Epinephrine / Vasoconstrictor and hypertensive effect antagonized

How Supplied: Powder for injection: 5 mg

Dosage
?IV, IM Prevent hypertension in pheochromocytoma, preoperative.
Adults, IV: 5 mg 1-2 hr before surgery; dose may be repeated if needed. Pediatric, IV, IM: 1 mg (or 0.1 mg/kg) 1-2 hr before surgery; dose may be repeated if needed.
Prevent or control hypertension during surgery.
Adults, IV: 5 mg. IV infusion: 0.5-1 mg/min. Pediatric, IV: 0.1 mg/kg (3 mg/m ²). May be repeated, if necessary. During surgery 5 mg for adults and 1 mg for children may be given to prevent or control symptoms of epinephrine intoxication (e.g., paroxysms of hypertension, respiratory depression, seizures, tachycardia).
Dermal necrosis/sloughing following IV or extravasation of norepinephrine.
Prevention: 10 mg/1,000 mL norepinephrine solution; treatment: 5-10 mg/10 mL saline injected into area of extravasation within 12 hr. Pediatric: 0.1-0.2 mg/kg to a maximum of 10 mg.
CHF.
Adults, IV infusion: 0.17-0.4 mg/min.
Diagnosis of pheochromocytoma.
Adults, rapid IV, initial: 2.5 mg (if response is negative, a 5-mg test should be undertaken before concluding the test is negative); children, rapid IV: 1 mg. Adults, IM: 5 mg; children, IM: 3 mg.
?Intracavernosal Impotence.
Adults: Papaverine, 30 mg, and 0.5-1 mg phentolamine; adjust dose according to response.