Pain relief with lidocaine 5% patch in localized peripheral neuropathic pain in relation to pain phenotype

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SCIENCE
Pain relief with lidocaine 5% patch in localized peripheral neuropathic pain in relation to pain phenotype
Key Take-Away: 

Lidocaine is an amide type local anesthetic medication and its efficacy in post neuropathic pain (PHN) with irritable nociceptor phenotype still need to be explored. This study was a great success in estimating its efficacy in PHN patients with irritable nociceptor phenotype.

In neuropathic pain with irritable nociceptor phenotype, up-regulation of sodium channels on nociceptors is supposed to be an important pain mechanism that may be targeted by topical sodium channel blockade.

ABSTRACT: 
Background: 

In neuropathic pain with irritable nociceptor phenotype, up-regulation of sodium channels on nociceptors is supposed to be an important pain mechanism that may be targeted by topical sodium channel blockade.

Methods: 

This randomized, double-blind, phenotype-panel, cross-over study with 4-week treatment periods of lidocaine 5% patch and placebo was performed to search for phenotype differences in effect.

The primary efficacy measure was the total pain intensity on an 11-point numeric rating scale (NRS), and the primary objective was to compare the effect of lidocaine in patients with and without irritable nociceptor phenotype as defined by hypersensitivity and preserved small fibre function determined by quantitative sensory testing. Forty-six patients with neuropathic pain due to nerve injury or postherpetic neuralgia were randomized. The modified intention-to-treat population comprised 15 patients with irritable nociceptor and 25 patients with non-irritable nociceptor. 

Results: 

In the total sample, lidocaine reduced pain by 0.3 NRS points (95% CI 0.1;0.5) and pain-related sleep disturbance by 0.6 points (95% CI 0.4;0.8) more than placebo (p=0.007 and p<0.001), and relieved pain by 0.4 verbal score (-1 to 5) points more (p=0.036).

For these measures, there was no significant interaction between treatment and phenotype, but there was a significant interaction for pain paroxysms (0.8, 95% CI 0.4;1.2, p<0.001) and deep aching pain (0.6, 95% CI 0.1;1.0, p=0.013).

 

 

Conclusion: 

Lidocaine 5% patch had an effect on peripheral neuropathic pain, and it may be most efficacious in patients with irritable nociceptor phenotype.

The lack of significant phenotype differences may be caused by too low statistical power.

 

Pain. 2015 Jun 18
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