Intravenous lidocaine in central pain - A double-blind, placebo-controlled, psychophysical study

Objective: To investigate the effects of systemic administration of lidocai ne on different components of neuropathic central pains by quantitative sen sory testing. Methods: The efficacy of systemic lidocaine (5 mg/kg IV over 30 minutes) was evaluated in a double-blind, placebo-controlled, and cross- over fashion, on both spontaneous ongoing pain and evoked pains (allodynia and hyperalgesia) in 16 patients with chronic poststroke (n = 6) or spinal cord injury (n = 10) related pain. Results: Lidocaine was significantly sup erior to the placebo (saline) in reducing the intensity of spontaneous ongo ing pain for up to 45 minutes after the injection: 10 of 16 patients (62.5% ) receiving lidocaine showed a significant reduction in spontaneous pain, w hereas only six patients showed this after the placebo. Lidocaine also sign ificantly reduced the intensity of brush-induced allodynia and mechanical h yperalgesia, but was no better than the placebo against thermal allodynia a nd hyperalgesia. In general, the side effects were moderate and consisted m ainly of lightheadedness (44%), Conclusions: Systemic lidocaine can induce a significant and selective reduction of several components of pain caused by CNS injuries. The observed preferential antihyperalgesic and antiallodyn ic effects of this drug suggest a selective central action on the mechanism s underlying these evoked pains.