Phentolamine

Administration

• Type: [[α₁ Blocker]]; Antidote, Extravasation; Antihypertensive
• Routes of Administration: IV, IM
• Common Trade Names: OraVerse

Adult Dosing

• Pheochromocytomectomy adjunct: 5mg IM/IV q2-4h PRN
  • Start: 1-2h preop

• Extravasation (norepinephrine-associated): 5-10mg injected into affected area x1
  • Start: within 12h of extravasation

• Hypertensive crisis: 5mg IM/IV q2-4h PRN

Pediatric Dosing

• Pheochromocytomectomy adjunct: 1mg IM/IV q2-4h PRN
  • Start: 1-2h preop

Special Populations

• Pregnancy Risk Factor: C

Renal Dosing

• No dosing adjustments

Hepatic Dosing

• No dosing adjustments

Contraindications

• Hypersensitivity to phentolamine or components
• MI
• CAD
• Angina
• Caution if PUD

Adverse Reactions

Serious

• MI
• stroke
• hypotension, severe
• arrhythmias
• PUD
• priapism

Common

• tachycardia
• weakness
• dizziness
• flushing
• orthostatic hypotension
• nasal congestion
• nausea
• vomiting
• diarrhea

Pharmacology

• Half-life: 19 minutes
• Metabolism: Urine
• Excretion: CYP450

Mechanism of Action

• α antagonist

References

<Epocrates, UpToDate>