Phentolamine


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : IV Hypertension in phaeochromocytoma 2-5 mg. Repeat if needed. IV/IM Diagnosis of pheochromocytoma 2.5-5 mg. Inj Dermal necrosis associated w/ norepinephrine IV infusion Prevention: Add 10 mg to each liter of soln containing norepinephrine. Treatment: Inject 5-10 mg (in 10 mL normal saline) into the affected area.
Dosage Details
Injection
Dermal necrosis associated with norepinephrine IV infusion
Adult: Prevention: 10 mg is added to each liter of solution containing norepinephrine. Treatment of extravasation: Inject 5-10 mg in 10 ml normal saline into the affected area.
Child: Treatment: Infiltrate area with 0.1 to 0.2 mg/kg (max 10 mg).

Intravenous
Hypertension in phaeochromocytoma
Adult: 2-5 mg. Repeat if necessary. Monitor BP.
Child: 1 mg IM/IV 1-2 hr before surgery. During surgery, 1 mg IV as indicated.

Parenteral
Diagnosis of pheochromocytoma
Adult: 2.5-5 mg IM/IV.
Child: 1 mg IV or 3 mg IM.
Contraindications
Renal impairment, coronary or cerebral arteriosclerosis, concurrent use with phosphodiesterase-5 (PDE-5) inhibitors including sildenafil (>25 mg), tadalafil, or vardenafil.
Special Precautions
Tachycardia or history of cardiac arrhythmias; gastritis or peptic ulcer disease; pregnancy and lactation. Discontinue if symptoms of angina occur or worsen.
Adverse Reactions
Orthostatic hypotension, tachycardia, flushing, sweating, feelings of apprehension, anginal pain, arrhythmias, nausea, vomiting, diarrhoea, weakness, dizziness, nasal congestion.
Potentially Fatal: MI, cerebrovascular spasm or occlusion.
IM/IV/Parenteral: C
Overdosage
Hypoglycaemia; severe hypotension, tachycardia, vomiting, dizziness. If fluid replacement is inadequate to treat hypotension, only alpha-adrenergic vasopressors such as norepinephrine should be used. Mixed agents such as epinephrine may cause more hypotension.
Drug Interactions
Epinephrine, ephedrine: effects may be decreased; ethanol: increased toxicity (disulfiram reaction).
Potentially Fatal: Additive BP-lowering effects with sildenafil, tadalafil or vardenafil.
Action
Description: Phentolamine is a reversible (competitive) and non-selective alpha-adrenergic receptor blocker, producing brief antagonism of circulating epinephrine and norepinephrine to reduce hypertension caused by alpha effects of these catecholamines. It has direct action on vascular smooth muscle; and has positive inotropic and chronotropic effects on the heart as well.
Onset: IM: 15-20 min; IV: immediate.
Duration: IM: 30-45 min; IV: 15-30 min.
Pharmacokinetics:
Metabolism: Hepatic.
Excretion: Metabolism: Hepatic. Via urine (10% as unchanged drug); half-life elimination: 19 min.
Storage
The reconstituted solution should be used upon preparation and should not be stored. Store unopened vials at controlled room temperature (59-86°F).
Disclaimer: This information is independently developed by MIMS based on Phentolamine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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