The safety of intravenous phentolamine administration in patients with neuropathic pain.

Abstract

The safety of intravenous (i.v.) infusion of large doses of phentolamine as an outpatient diagnostic tool for sympathetically maintained pain was studied retrospectively in 100 consecutive patients (73 females and 27 males) with chronic pain. All patients were pretreated with i.v. fluids followed, in most cases, by propranolol, 1-2 mg i.v. (n = 95). Ten minutes later the phentolamine infusion commenced, lasting for 20 min. In 90 patients, the dose of phentolamine was 35 mg. Two patients received 25 mg, and 8 patients received larger doses of 50-75 mg. No major complications occurred during or after the test, and only small changes in arterial blood pressure or heart rate were observed. All patients developed mild nasal stuffiness, but no decline in oxygen saturation was observed. Five patients developed one of the following minor complications for a brief duration, that resolved spontaneously: sinus tachycardia, premature ventricular beats, dizziness, or wheezing. We conclude that i.v. phentolamine administration is safe in patients with neuropathic pain.