PURPOSE: Neuropathic pain, resulting from injury to the peripheral or central nervous system, is due to upregulation of aberrant sodium channels with neuronal hyperexcitability. Lidocaine blocks these channels and several studies show that intravenous (IV) lidocaine infusion provides significant relief in patients with chronic peripheral neuropathic pain in the short term (for up to six hours). Our objective was to determine if IV lidocaine provides significant pain relief and overall improvement in quality of life in the longer term (for up to four weeks).
METHODS: This single site randomized double-blind, crossover trial compared IV lidocaine infusion (5 mg·kg-1) with active placebo infusion containing diphenhydramine (50 mg) in patients with chronic neuropathic pain of peripheral nerve origin of at least six months duration. The primary outcome was average pain intensity reduction from IV lidocaine relative to placebo at four weeks post-infusion. Secondary outcome measures included parameters of physical function, mood, and overall quality of life.
RESULTS: We enrolled 34 subjects in this trial-mostly with painful diabetic neuropathy and post-herpetic neuralgia. There were no significant differences between IV lidocaine and placebo infusions at any time point involving any of the outcome measures. Mean (standard deviation) pain intensity at week 4 for the placebo and lidocaine groups were not different [6.58 (1.97) vs 6.78 (1.56), respectively; between-group difference, 0.17; 95% confidence interval, - 0.50 to 0.84].
CONCLUSION: We found no significant long-term analgesic or quality of life benefit from IV lidocaine relative to control infusion for chronic peripheral neuropathic pain.
TRIAL REGISTRATION: clinicaltrials.gov (NCT01669967); registered 22 June, 2012.
Further safe and effective treatments of neuropathic pain are needed. Lidocaine infusion has been suggested as one alternative. The present study with a cross-over design could however not verify any positive effects in patients with chronic neuropathic pain.
As a pain clinican with more than 20 years of experience using lidocaine infusions, these results are surprising. At least, a rate of 40% of significant long-term (2-3 months) good outcome would be expected. An explanation could be the single-dose protocol of lidocaine administration, instead of the more usual based on 3 to 7 doses on different days.
As other raters have state, this seems a little surprising. I am curious what the baseline scores were for both groups and whether there was a meaningful reduction in pain at all. With 6 months or more of pain, I would expect central factors and psychosocial factors, in addition to the peripheral neuropathic pain. In which case, there could be a strong component of nonspecific treatment effect driving pain reduction. However, it is not clear from the abstract what the starting values were, or what amount of pain relief (30%, 50%?) was expected.