The safety and efficacy of intrathecal adenosine in patients with chronic neuropathic pain

Adenosine and adenosine analogs decrease pain-like behavior in animal model s of both acute nociceptive and neuropathic pain via adenosine receptor act ivation at spinal and/or supraspinal levels. This open study is the first i n a series of intrathecal (IT) adenosine administration studied for the eva luation of efficacy and side effects in 14 patients All had chronic neuropa thic pain with tactile hyperalgesia and/or allodynia primarily of traumatic origin. The effects of IT adenosine (500 mu g [n = 9] or 1000 mu g [n = 5] ) were evaluated. Approximate areas of tactile pain were mapped. Spontaneou s and evoked pain (visual analog scale score 0-100) and tactile pain thresh olds were assessed before and 60 min after injection. The injection caused transient pain (<60 min) in the lumbar region in five patients. There were no other side effects. Spontaneous and evoked pain was reduced (median scor e from 65 to 24 [P < 0.01] and from 71 to 12 [P < 0.01], respectively) in p arallel with increased tactile pain thresholds in allodynia areas. Areas of tactile hyperalgesia/allodynia were reduced (median reduction 90%; P < 0.0 01). Twelve patients experienced pain relief (median 24 h). We conclude tha t IT adenosine transiently causes lumbar pain in a subgroup of patients and may reduce various aspects of chronic neuropathic pain. Implications: This is the first series of patients with chronic neuropathic pain in which tol erability to spinal adenosine administration has been evaluated. A subset o f patients reported transient low back pain as the only side effect. Sponta neous and evoked pain intensity decreased in most patients, an effect lasti ng for a median of 24 h.