Phentolamine

Phentolamine is a prescription medication used for the prevention or control of hypertensive (high blood pressure) episodes that may occur in a patient with pheochromocytoma as a result of stress or manipulation during preoperative preparation and surgical excision, for the prevention or treatment of dermal necrosis and sloughing following intravenous administration or extravasation of norepinephrine, and the diagnosis of pheochromocytoma by the phentolamine blocking test.

• Phentolamine is available under the following different brand names: Regitine, OraVerse

Adult and pediatric dosage

Powder for injection

• 5mg
• Injectable solution
• 0.4mg/1.7mL
• Pheochromocytoma
• Adult and geriatric dosage
• Diagnosis: 5 mg IV/IM
• Test for pheochromocytoma is positive if decrease SBP is more than 35 mmHg & decrease DBP is more than 25 mmHg
• Pediatric dosage
• 0.1-0.2 mg/kg IV/IM, OR 1 mg IV OR 3 mg IM 
• Pheochromocytoma Surgery Use
• Adult and geriatric dosage
• 5 mg IV/IM 1-2 hours preoperative, repeat if necessary every 2-4 hours
• Pediatric dosage
• 0.05-0.1 mg/kg/dose OR 1 mg IV/IM 1-2 hours preoperative, repeat every 2-4 hours until hypertension is controlled; not to exceed 5 mg/dose 
• Extravasation Treatment
• Adult and geriatric dosage
• Treatment: 5-10 mg in 10 mL NS local injection within 12 hours
• Prevention: 10 mg for each liter of IV fluids (pressor effect of NE is unaffected)
• Pediatric dosage
• 0.1-0.2 mg/kg to no more than 10 mg
• Dental Anesthesia Reversal (OraVerse)
• Adult and geriatric dosage
• Dose based on the amount of local anesthetic administered
• Administer using the same locations and techniques (infiltration or block injection) as a local anesthetic
• 1/2 cartridge local anesthetic: OraVerse 1/2 cartridge (0.2 mg)
• 1 cartridge local anesthetic: OraVerse 1 cartridge (0.4 mg)
• 2 cartridges local anesthetic: OraVerse 2 cartridges (0.8 mg)

Pediatric dosage

• Children below 6 years or less than 15 kg: Safety and efficacy not established
• Dose based on the amount of local anesthetic administered
• Administer using the same locations and techniques (infiltration or block injection) as a local anesthetic
• Children between 6 to 12 years or 15 to 30 kg: For 1/2 cartridge local anesthetic, use OraVerse 1/2 cartridge (0.2 mg)
• Children between 6 to 12 years or more than 30 kg:
• 1/2 cartridge local anesthetic: OraVerse 1/2 cartridge (0.2 mg)
• 1 cartridge local anesthetic: OraVerse 1 cartridge (0.4 mg)

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

Common side effects of Phentolamine include:

• acute and prolonged hypotensive episodes,
• fast heart rate,
• cardiac arrhythmias,
• weakness,
• dizziness,
• flushing,
• dizziness upon standing (orthostatic hypotension),
• stuffy nose,
• nausea,
• Injection site pain,
• vomiting, and
• diarrhea.

Serious side effects of Phentolamine include:

• chest pain,
• myocardial infarction, 
• cerebrovascular spasm, and
• cerebrovascular occlusion.

Rare side effects of Phentolamine include:

• none 

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Phentolamine has severe interactions with no other drugs.
• Phentolamine has serious interactions with the following drugs:
  • lofexidine
  • sildenafil
  • tamsulosin
  • vardenafil
  • yohimbe
• Phentolamine has moderate interactions with at least 93 other drugs.
• Phentolamine has minor interactions with the following drugs:
  • brimonidine
  • butcher's broom
  • ethanol
  • phenylephrine
  • phenylephrine PO
  • tizanidine
  • treprostinil

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

Contraindications

• Hypersensitivity; MI or other CAD

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Phentolamine?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Phentolamine?”

Cautions

• The first dose effect may occur, causing a sudden and drastic fall in blood pressure after administering the first dose.
• Hypotension/syncope with the first few doses or with an increase in dose; minimize by using a small first dose at bedtime
• Increase dose slowly
• Myocardial infarction, cerebrovascular spasm, and cerebrovascular occlusion were reported following parenteral administration of phentolamine; these events usually occurred in association with marked hypotensive episodes producing shock-like states
• Tachycardia and cardiac arrhythmias may occur with the use of phentolamine or other alpha-adrenergic blocking agents; although such effects are uncommon after administration, clinicians should be alert to signs and symptoms of these events, particularly in patients with a prior history of cardiovascular disease; discontinue if angina occur or worsen

Pregnancy and Lactation

• Use with caution if the benefits outweigh the risks during pregnancy.

Lactation

• Not known if excreted in breast milk; not recommended