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.

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).

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.

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

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.

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).

Availability ⬆ ⬇

(Generic available)

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

Assessment ⬆ ⬇

Monitor BP, pulse, and ECG every 2 min until stable during IV administration. If hypotensive crisis occurs, epinephrine is contraindicated and may cause paradoxic further decrease in BP; norepinephrine may be used.

Implementation ⬆ ⬇

Patient should remain supine throughout parenteral administration.
Infiltration: Dilute 5–10 mg of phentolamine in 10 mL of 0.9% NaCl. For children, use 0.1–0.2 mg/kg up to a maximum of 10 mg. Infiltrate site of extravasation promptly. Must be given within 12 hr of extravasation to be effective.

IV Administration:

IV: Diluent: Reconstitute each 5 mg with 1 mL of sterile water for injection or 0.9% NaCl. Discard unused solution.Concentration: 5 mg/mL.
Rate: Inject each 5 mg over 1 min.
Dilute 5–10 mg in 500 mL of D5W.
Rate: Titrate infusion rate according to patient response.
- May also add 10 mg to every 1000 mL of fluid containing norepinephrine for prevention of dermal necrosis and sloughing. Does not affect pressor effect of norepinephrine.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇