Topical Lidocaine: Predictors of Response in Peripheral Nerve Injury

Evaluation of Predictors of Response for the Efficacy of Topical Lidocaine Patch (Versatis) on Chronic Neuropathic Pain After Peripheral Nerve Injury

The primary purpose is to study the predictive value of preserved nociceptors and large afferent fibers and dynamic mechanical allodynia on the effect of lidocaine patch. The primary outcome measure is the predictive role for these three measures for obtaining a response to lidocaine. A responder is defined as a person with at least a 2-point pain reduction to lidocaine (change in median pain intensity (measured on a 10 point numeric rating scale) of pain from the baseline week to the last week of lidocaine treatment). Secondary effect variable will be efficacy of lidocaine on pain reduction (baseline week versus last week of each treatment) and pain relief (complete, good, moderate, slight, none, or worse) for spontaneous and evoked pain, and effect on ongoing pain, brush evoked allodynia, cold and warm allodynia, and pinprick hyperalgesia evaluated on each visit.

Inclusion Criteria:

• patients aged 18 or more with neuropathic pain after a peripheral nerve injury with a pain intensity of at least 4 on a 0-10 point numeric rating scale.

Exclusion Criteria:

• pregnancy or lactation,
• allergy to lidocaine,
• alcohol abuse,
• psychiatric disorders,
• skin diseases in the area where the patches are to be applied,
• treatment with class I antiarrhythmic agents,
• any treatment within the past one month or concomitantly with Na2+-channel blockers (e.g., mexiletine, phenytoine, propafenone),
• any topical treatment with capsaicin within the last three months before entering the study, or any other topical treatment in the area of neuropathic pain,
• concomitant therapy with TENS or acupuncture.