phentolamine

REMS

IV: Control of BP during surgical removal of a pheochromocytoma.

IV, Infiltration

Prevention and treatment of dermal necrosis and sloughing following extravasation of norepinephrine, phenylephrine, or dopamine.

Local

Reversal of soft-tissue anesthesia (of lip and tongue) resulting from an intraoral submucosal injection of a local anesthetic containing a vasconstrictor.

Unlabeled Use:

IV: Hypertension associated with pheochromocytoma or adrenergic (sympathetic) excess, such as administration of phenylephrine, tyramine-containing foods in patients on MAO inhibitor therapy, or clonidine withdrawal.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Coronary or cerebral arteriosclerosis;
Renal impairment.

Use Cautiously in:

Peptic ulcer disease;
OB: Safety not established in pregnancy;
Lactation: Safety not established in breastfeeding;
Pedi: Children <3 yr or <15 kg (Oraverse) (safety and effectiveness not established);
Geri: Older adults are more susceptible to hypotensive effects; ↓ dose recommended.

Adv. Reactions/Side Effects ⬆ ⬇

With IV use

CV: angina, arrhythmias, hypotension, MI, tachycardia

Derm: flushing

EENT: nasal stuffiness

GI: abdominal pain, diarrhea, nausea, vomiting, aggravation of peptic ulcer

Local: injection site pain (local)

Neuro: CEREBROVASCULAR SPASM, dizziness, weakness

Interactions ⬆ ⬇

Drug-drug:

Antagonizes the effects of alpha-adrenergic stimulants.
May ↓ pressor response to ephedrine or phenylephrine.
Severe hypotension may occur with concurrent use of epinephrine.
↓peripheral vasoconstriction from high doses of dopamine.

Availability ⬆ ⬇

(Generic available)

Powder for injection: 5 mg/vial
Injection for local infiltration/block injection: 0.4 mg/cartridge

Route/Dosage ⬆ ⬇

Hypertension Associated with Pheochromocytoma—Before/During Surgery

IV (Adults ): 5 mg given 1–2 hr preoperatively, repeated as necessary. May be infused at a rate of 0.5–1 mg/min during surgery.
IV IM (Children ): 1 mg or 0.1 mg/kg (3 mg/m²) given 1–2 hr preoperatively, repeated IV as necessary during surgery.

Prevention of Dermal Necrosis during Infusion of Norepinephrine, Phenylephrine, or Dopamine

IV (Adults ): Add 10 mg phentolamine to every 1000 mL of fluid containing norepinephrine.

Treatment of Dermal Necrosis Following Extravasation of Norepinephrine, Phenylephrine, or Dopamine

Infiltrate(Adults ): 5–10 mg.
Infiltrate(Children ): 0.1–0.2 mg/kg (up to 10 mg).

Reversal of Intraoral Submucosal Anesthesia Following Dental Procedures (Oraverse)

Infiltrate or Block Injection(Adults and Children ≥3 yr and >30 kg): Dose administered is based on number of cartridges of local anesthetic with vasoconstrictor administered: ½cartridge local anesthetic: 0.2 mg phentolamine (½ cartridge); 1 cartridge local anesthetic: 0.4 mg phentolamine (1 cartridge); 2 cartridges local anesthetic: 0.8 mg phentolamine (2 cartridges).
Infiltrate or Block Injection(Children ≥3 yr and 15–30 kg): Do not exceed dose of 0.2 mg (½ cartridge).

US Brand Names ⬆ ⬇

Action ⬆ ⬇

Produces incomplete and short-lived blockade of alpha-adrenergic receptors located primarily in smooth muscle and exocrine glands.
Induces hypotension by direct relaxation of vascular smooth muscle and by alpha blockade.
Increases blood flow to submucosal tissue through blockade of alpha receptors.

Therapeutic effects:

Reduction of BP in situations in which hypertension is due to adrenergic (sympathetic) excess.
When infiltrated locally, reverses vasoconstriction caused by norepinephrine or dopamine.
Reverses local anesthetic effects (restores normal lip and tongue sensation).

Classifications ⬆ ⬇

Therapeutic Classification: antidotes, antihypertensives

Pharmacologic Classification: alpha adrenergic blockers

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following IM administration; IV administration results in complete bioavailability; completely available after local injection.

Distribution: Unknown.

Metabolism/Excretion: 10% excreted unchanged by kidneys.

Half-Life: IV: 19 min; Local injection: 2–3 hr.

Canadian Brand Names ⬆ ⬇

Time/Action Profile ⬆ ⬇

(alpha-adrenergic blockade)

ROUTE	ONSET	PEAK	DURATION
IM	unknown	20 min	30–45 min
IV	immediate	2 min	15–30 min
Local	rapid	10–20 min	unknown

Patient/Family Teaching ⬆ ⬇

Advise patient to change positions slowly to minimize orthostatic hypotension.
Instruct patient to notify health care professional if chest pain occurs during IV infusion.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

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Indications ⬇