IV Lidocaine Helpful for Mechanical Allodynia

Dave ARNP · Feb 29, 2004

Laurie Barclay, MD

Feb. 2, 2004-Intravenous (IV) lidocaine is helpful for mechanical allodynia, according to the results of a randomized trial published in the Jan. 27 issue of Neurology.

"We have previously shown, using quantitative sensory tests, that IV lidocaine induced selective and differential analgesic effects in patients with central neuropathic pain," write N. Attal, MD, PhD, from Université Versailles-Saint-Quentin in France, and colleagues. "Thus the treatment alleviated spontaneous pain and mechanical allodynia/hyperalgesia, but had no effect on thermal allodynia/hyperalgesia. This argued against a generalized effect on pain perception, but rather emphasized that lidocaine presented with specific antiallodynic and antihyperalgesic effects in such patients."

In this double-blind, crossover design study, 22 patients with pain caused by postherpetic neuralgia or nerve trauma received lidocaine, 5 mg/kg IV, or placebo infusion over 30 minutes and were evaluated using quantitative sensory testing. On an open-label basis, 16 patients subsequently received mexiletine titrated from 400 to 1,000 mg per day (mean, 737 mg/day).

Lidocaine significantly decreased ongoing pain for up to six hours, with a peak effect 60 to 120 minutes after injection. It also decreased mechanical dynamic allodynia and static or punctate mechanical allodynia/hyperalgesia, but not thermal allodynia and hyperalgesia, suggesting that the analgesic effects of the drug were modality-specific.

Compared with patients without allodynia, those with concomitant mechanical allodynia had significantly greater effects from lidocaine and mexiletine on spontaneous pain intensity.

The authors suggest that patients with mechanical allodynia may be good candidates for treatment with local anesthetic-like drugs and possibly with other sodium-channel blockers.

"The usual definition of a responder to a certain drug in the context of neuropathic pain, although it has the advantage of simplicity and permits a clinical comparison between different drugs, is probably too broad and may lack sensitivity," they write. "Our study highlights that the response to a drug rather depends on a combination of symptoms that may relate to specific common mechanisms and favors the importance of a mechanism-based classification of neuropathic pains."

The Institut UPSA de la Douleur supported this study.

Neurology. 2004;62:218-225

Reviewed by Gary D. Vogin, MD

http://www.medscape.com/viewarticle/468048