Systemic ATP infusion improves spontaneous pain and tactile allodynia, but not tactile hypesthesia, in patients with postherpetic neuralgia.

Abstract

Activation of purinoceptors may improve neuropathic pain. Accordingly, the effects of systemic ATP infusion were assessed in patients with postherpetic neuralgia (PHN). Eight patients with PHN lasting over 3 months were enrolled. Initially, patients received the vehicle (20% dextrose) or ATP (at a dose of 1 mg x kg(-1) in 20% dextrose) infused intravenously for 60 min on two separate occasions in a single-blinded manner. The levels of spontaneous continuous pain, paroxysmal pain, and tactile allodynia were assessed by a visual analogue scale (VAS), and tactile hypesthesia was assessed by Semmes-Weinstein monofilament before and after infusion. Subsequently, the eight patients received an ATP infusion (1 mg.kg(-1) in 20% dextrose) once a week for 5-12 weeks in an open-label manner, and changes in the above parameters were assessed. In the initial study, VAS for spontaneous continuous pain and tactile allodynia decreased significantly with ATP infusion but not with placebo infusion. After repeated ATP infusions for 5-12 weeks, the median VAS for spontaneous continuous pain, paroxysmal pain, and tactile allodynia decreased significantly from 32.1 to 13.0, from 46.9 to 17.5, and from 49.5 to 15.6 respectively. However tactile hypesthesia did not improve significantly. This study demonstrated that repetitive intravenous ATP infusion could improve spontaneous continuous pain and paroxysmal pain, as well as improving tactile allodynia, but did not influence tactile hypesthesia.