- 10mg/1ml ampules (subcutaneous)
- 5mg lyophilized powder (subcutaneous)

Executive Summary

(April 19, 2023)

Phentolamine is a vasodilator used to prevent tissue necrosis caused by extravasated catecholamine infusions (epinephrine, norepinephrine, dopamine, etc). Available in the US. Limited stock in Canada. Unavailable in Chile. 

Adult dose for vasopressor extravasation:
5-10mg diluted in 10-20ml of NaCl 0.9% subcutaneous immediately after extravasation (use within 12 hours). 

Mechanism of Action and Usage

Mechanism of Action

Phentolamine is a potent and short-acting non-selective alpha blocker (alpha-1 and alpha-2). Alpha-1 blockade reduces peripheral resistance, and alpha-2 blockade causes cardiac stimulation due to an enhanced release of norepinephrine from sympathetic nerves, with subsequent inotropic and chronotropic effects. 


It is used to prevent tissue ischemia caused by extravasation of norepinephrine and other alpha agonists (1, 3), obtaining the FDA approval in 1998 (2). From the safety patient perspective it is recommended to have an extravasation protocol in the hospital services where vasopressors are used (3), and in retrospective studies phentolamine use is associated with favorable outcomes (4, 5). It is also indicated to diagnose pheochromocytoma disease and to prevent and treat pheochromocytoma-related hypertensive crises (1). 

Adult dose

Injection site vasopressor extravasation

Phentolamine 5 to 10mg in 10mL of normal saline,  subcutaneous within 12 hours into the area of extravasation. Any visible hyperemia and increased tissue warmth at the site of extravasation are signs of effective treatment. 

Pediatric dose

Injection site vasopressor extravasation

Renal, hepatic, or other adjustments

No adjustments required. 

Dosage Forms and brand names


The following issues of concern are related mostly to  endovenous administration of phentolamine. Consider that subcutaneous use in extravasation is intended to cause local effects rather than systemic effects. The following issues of concern are related to IV administration. 

Pregnancy and Lactation

Consider that subcutaneous use in extravasation is intended to cause local effects rather than systemic effects, with an hypothetical low risk for the fetus or infant. 


Alpha-adrenergic block of relatively short duration. Also direct but less marked positive inotropic and chronotropic effects. The pharmacokinetics of phentolamine are largely unknown. 

Following specifications are not applicable to subdermic administration:


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