SYSTEMIC ADENOSINE INFUSION ALLEVIATES SPONTANEOUS AND STIMULUS-EVOKED PAIN IN PATIENTS WITH PERIPHERAL NEUROPATHIC PAIN

In seven patients with peripheral neuropathic pain, the effect of syst emic adenosine infusion on pain symptoms was evaluated in a double-bli nd, placebo controlled, cross-over study. The study infusions, adenosi ne (50 mu g . kg(-1). min(-1)) or placebo, were given intravenously (I V) during 45-60 min at two separate occasions. Before and during infus ions, bedside examination of sensibility and quantitative sensory test ing (QST), i.e., assessments of perception thresholds for touch, touch -evoked pain, cold, warmth, painful heat, and cold, were performed. In the neuropathic area, sensation magnitude was rated by a visual analo g scale (100 mm VAS) using a pin and at perception threshold for touch -evoked pain using von Frey filaments. Adenosine infusion reduced spon taneous pain (P < 0.05), and caused an increase of the touch-evoked pa in threshold from 10.8 +/- 5.3 to 22.2 +/- 6.9 g (P < 0.05), whereas p lacebo had no effect. Pain intensity at perception threshold for touch -evoked pain was, however, unaltered. Pinprick-evoked pain in the neur opathic areas was reduced from 53 +/- 11 to 29 +/- 10 mm (P < 0.05). N o other sensory modality was consistently changed during adenosine inf usion. In conclusion, the present study demonstrates that adenosine in fusion alleviates spontaneous neuropathic pain, tactile allodynia, and pinprick hyperalgesia in patients with peripheral neuropathic disorde rs, probably by a central mechanism of action.