Dose:   0.1 to 0.2 mg/kg/dose IV, intradermal (see comments)

Comments: Phentolamine is used for local treatment for extravasation of dopamine (or other vasoconstrictors) and treatment of hypertension due to pheochromocytoma. Since phentolamine competitively blocks alpha-adrenergic receptors, the relaxation of the vascular smooth muscle will be associated with a hyperemic response (Flemmer and Chan. Pediatr Nurs 1993; 19:355). Inject the diluted solution (see preparation) directly into the area of extravasation within 12 hours. Suggested maximum dose for children is 0.1 to 0.2 mg/kg (Facts and Comparisons, Inc. Drug Facts and Comparisons. Olin, B.R. ed. St. Louis, MO:Facts and Comparisons, Inc; 1997, page 166). When used as an antihypertensive agent  due to pheochromocytoma the suggested dose for children (either for diagnosis or treatment) is 1 mg IV or IM.

    Phentolamine may also be useful in the treatment of naloxone induced pulmonary edema. Brimacombe (Anaesth Intensive Care 1991; 19:578) reported two cases of acute pulmonary edema following use of naloxone in an adolescent and an adult. The pulmonary edema was thought to be due to a centrally mediated massive catecholamine response leading to a shift of blood volume into the pulmonary vascular bed. The use of phentolamine reversed the pulmonary edema though a brief continuous infusion was required in one patient. He suggested that naloxone-induced pulmonary edema was similar to Irukandji syndrome (a syndrome of massive pulmonary edema caused by envenomization by the jellyfish Carukia barnesi that produces massive catecholamine release) and that alpha-blockade produced by phentolamine may be worthwhile its management.

Preparation: Phentolamine (Regitine) is available in 1 ml vials (5 mg/ml) with 25 mg of mannitol. A 0.5 mg/ml solution is prepared by mixing 5 mg of phentolamine in 9 ml of normal saline.  The solution should be used once and discarded.

Compatibility: Compatible with D5W, NS, amiodarone, and dobutamine.