Phentolamine

Phentolamine is a prescription medication used to reverse numbness after oral and dental procedures, to prevent and control episodes of dangerously high blood pressure, to prevent and treat accidental injection of certain drugs under the skin, and also to diagnose a condition called pheochromocytoma.

Phentolamine belongs to a group of medications called vasodilators. These drugs work by causing blood vessels to expand and allow more blood to flow through them.

Phentolamine is available in an injectable form to be given by a healthcare professional directly into tissue of the mouth, a muscle, or a vein depending on the condition being treated or diagnosed.

Common side effects of phentolamine include injection site pain, headache, and changes in heart rate.

Phentolamine can also cause dizziness. Do not drive or operate heavy machinery until you know how phentolamine affects you.

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• acetaminophen
• alfentanil
• alfuzosin
• alprazolam
• aluminum hydroxide
• amifostine
• aminophylline
• amitriptyline
• ammonium chloride
• amobarbital
• amoxapine
• amyl nitrite
• anhydrous calcium iodide
• apomorphine
• aripiprazole
• asenapine
• aspirin
• atropine
• avanafil
• baclofen
• belladonna
• brexpiprazole
• bromodiphenhydramine
• brompheniramine
• bupivacaine
• buprenorphine
• bupropion
• buspirone
• butabarbital
• butorphanol
• cabergoline
• canagliflozin
• carbetapentane
• cariprazine
• carisoprodol
• chloral hydrate
• chlorcyclizine
• chlordiazepoxide
• chlorpheniramine
• chlorpromazine
• chlorthalidone
• clobazam
• clomipramine
• clonazepam
• clonidine
• clorazepate
• clozapine
• codeine
• conjugated estrogens
• dapagliflozin
• dexmedetomidine
• dextromethorphan
• diazepam
• dihydrocodeine
• diphenhydramine
• doxepin
• droperidol
• dutasteride
• dyphylline
• empagliflozin
• ephedrine
• fenoldopam
• fentanyl
• fluoxetine
• fluphenazine
• flurazepam
• furazolidone
• garlic
• guaifenesin
• haloperidol
• hydromorphone
• hydroxyzine
• hyoscyamine
• ibuprofen
• iloperidone
• iloprost
• imipramine
• insulin products
• isocarboxazid
• licorice
• linezolid
• lithium
• lorazepam
• loxapine
• lurasidone
• maprotiline
• maraviroc
• meperidine
• meprobamate
• mesoridazine
• methadone
• methdilazine
• methocarbamol
• methotrimeprazine
• midazolam
• mirtazapine
• molindone
• morphine
• nalbuphine
• naloxone
• nefazodone
• nortriptyline
• olanzapine
• olopatadine
• orphenadrine
• oxazepam
• oxycodone
• paliperidone
• paraldehyde
• pentazocine
• pentoxifylline
• perphenazine
• phenelzine
• phenobarbital
• phenylephrine
• procarbazine
• prochlorperazine
• promazine
• promethazine
• propiomazine
• propoxyphene
• quetiapine
• rasagiline
• riociguat
• risperidone
• secobarbital
• selegiline
• sildenafil
• silodosin
• sodium nitrite
• tadalafil
• tamsulosin
• temazepam
• tetrabenazine
• thiethylperazine
• thioridazine
• thiothixene
• tizanidine
• tranylcypromine
• trazodone
• trifluoperazine
• triflupromazine
• trimeprazine
• trimipramine
• vardenafil
• verteporfin
• zaleplon
• ziprasidone
• zolpidem

 This is not a complete list of phentolamine drug interactions. Ask your doctor or pharmacist for more information.

Use phentolamine as ordered by your doctor. Read all information given to you. Follow all instructions closely.

• It is given as a shot.

What do I do if I miss a dose?

• Call your doctor to find out what to do.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Feeling tired or weak.
• Dizziness.
• Flushing.
• Stuffy nose.
• Upset stomach or throwing up.
• Loose stools (diarrhea).

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

• If you need to store this medicine at home, talk with your doctor, nurse, or pharmacist about how to store it.

Phentolamine Mesylate for Injection, USP is an antihypertensive, available in vials for intravenous and intramuscular administration. Each vial contains Phentolamine mesylate, USP, 5 mg, and mannitol USP, 25 mg, in sterile, lyophilized form.

Phentolamine Mesylate, USP is 4,5-dihydro-2-[N-(m-hydroxyphenyl)-N-(p-methylphenyl) amino methyl]-1H- imidazole 1:1 methanesulfonate, and its structural formula is

Phentolamine mesylate, USP is a white or off-white, odorless crystalline powder with a molecular weight of 377.46. Its solutions are acid to litmus. It is freely soluble in water and in alcohol, and slightly soluble in chloroform. It melts at about 178°C.

Phentolamine Mesylate for Injection, USP produces an alpha-adrenergic block of relatively short duration. It also has direct, but less marked, positive inotropic and chronotropic effects on cardiac muscle and vasodilator effects on vascular smooth muscle.

Phentolamine Mesylate for Injection, USP has a half-life in the blood of 19 minutes following intravenous administration. Approximately 13% of a single intravenous dose appears in the urine as unchanged drug.

Myocardial infarction, history of myocardial infarction, coronary insufficiency, angina or other evidence suggestive of coronary artery disease; hypersensitivity to Phentolamine or related compounds.

Extravasation of sympathomimetic vasopressors, treatment:

Manufacturer's labeling: Norepinephrine extravasation: Children and Adolescents: Local infiltration: Infiltrate area of extravasation with a small amount of a 0.5 to 1 mg/mL solution as soon as extravasation is noted but within 12 hours of extravasation

Alternate dosing: Extravasation of dopamine, epinephrine, norepinephrine, phenylephrine: Limited data available: Infants, Children, and Adolescents: SubQ: Infiltrate area of extravasation with a small amount (eg, 1 mL given in 0.2 mL aliquots) of a 0.5 to 1 mg/mL solution within 12 hours of extravasation (Flemmer 1993; Hill 1991; MacCara 1983; Montgomery 1999). Total dose required depends on the size of extravasation; dose may be repeated if required. When reported, the total dose needed was 1 to 5 mL of a 1 mg/mL solution; however, other concentrations could be used (Montgomery 1999).

Diagnosis of pheochromocytoma (phentolamine blocking test): Note: The phentolamine-blocking test for the diagnosis of pheochromocytoma has largely been supplanted by the measurement of catecholamine concentrations and catecholamine metabolites (eg, metanephrine) in the plasma and urine; reserve phentolamine for cases when additional confirmation is necessary to determine diagnosis:

Manufacturer's labeling: Children and Adolescents:

IM: 3 mg

IV: 1 mg

Alternate dosing: Limited data available: Children and Adolescents: IV: 0.05 to 0.1 mg/kg/dose, maximum single dose: 5 mg (Kliegman 2007)

Hypertensive episodes associated with pheochromocytoma, prevention and treatment: Note: In the perioperative period, the use of other agents may be preferred due to slow onset of action and prolonged duration of phentolamine in comparison to the other agents (eg, nitroprusside) (Miller 2010).

Preoperative: Children and Adolescents: IM, IV: 1 mg given 1 to 2 hours before surgery and repeat if needed

Intraoperative:

Manufacturer's labeling: Children and Adolescents: IV: 1 mg as indicated to prevent or control paroxysms of hypertension, tachycardia, respiratory depression, seizure, or other effects associated with epinephrine intoxication resulting from tumor manipulation

Alternate dosing: Limited data available: Infants, Children, and Adolescents: IV: 0.05 to 0.1 mg/kg/dose (Coté 2013). Note: Usual adult dose is 5 mg/dose (Miller 2010).

Reversal of oral soft tissue (lip, tongue) anesthesia (OraVerse): Note: Dose is based upon the number of cartridge(s) of local anesthetic administered; location and administration technique (infiltration or block injection) should be the same as used for local anesthetic administration.

Children ≥3 years weighing ≥15 kg and Adolescents: Submucosal oral injection: Infiltration or block technique:

Maximum dose:

15 to <30 kg: 0.2 mg/dose

≥30 kg: 0.8 mg/dose; Note: A dose of >0.4 mg has not been studied in children <4 years

There are no dosage adjustments provided in the manufacturer’s labeling.

Blood pressure, heart rate; monitor and document extravasation site; monitor patient for orthostasis; assist patient with ambulation

Consult your pharmacist.

How to use Phentolamine Powder

Consult your pharmacist.

Consult your pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.