Localized neuropathic pain symptoms are reported after knee surgery in 30% to 50% of patients. 5% lidocaine plaster (LP5) is recommended for localized neuropathic pain, but evidence in postsurgery neuropathic pain is missing. This study focuses on the effectiveness of LP5 on allodynia, hyperalgesia, and thermal stimuli in postsurgery knee localized neuropathic pain. A randomized double-blind, 2 parallel groups, controlled trial (NCT02763592) took place in 36 patients (age, 69.4 ± 7.3 years) at the Clinical Pharmacology Center, University Hospital Clermont-Ferrand, France. Patients randomly received LP5 or placebo plaster during 3 months. Neuropathic pain intensity and several parameters (dynamic mechanical allodynia, mechanical [von Frey], heat and cold detection and pain thresholds [Pathway Medoc], and size of the allodynic area were recorded at each visit [inclusion, day 7, 15, month 1, 2, and 3]). From day 7 onwards, dynamic mechanical allodynia diminished progressively of ≥ 30% over 3 months (P = 0.003) in 96% of patients (23/24) and of ≥ 50% in 83% of patients (20/24). Cold pain and maximal mechanical pain thresholds improved over 3 months (P = 0.001 and P = 0.007, respectively). This study shows for the first time the effectiveness of LP5 on dynamic mechanical allodynia, pain, pressure, and cold thresholds over 3 months in knee localized neuropathic pain. Beyond the inhibition of sodium channels by LP5, these findings suggest the involvement of cold and mechanical receptors that participate to pain chronicisation and also of the non-negligible placebo effect of the patch, items that need to be explored further and challenged in other etiologies of localized neuropathic pain.
This randomized double-blind controlled trial in 36 patients shows for the first time the effectiveness of 5% lidocaine plaster in postsurgery knee neuropathic pain.
aUniversité Clermont Auvergne Neurodol, Inserm 1107, Clermont–Ferrand, France
bClinical Pharmacology Department CPC/CIC Inserm 1405, University Hospital, CHU F-63000 Clermont–Ferrand, France
cHergan Consulting 4U, Courbevoie, France
dCHU Clermont-Ferrand, DRCI, Clermont-Ferrand, France
Corresponding author. Address: Centre de Pharmacologie Clinique, Bâtiment 3C, CIC Inserm 1405, CHU Clermont-Ferrand, BP 69, F-63003 Clermont-Ferrand Cedex 1, France. Tel.: (+33) 4 73 17 84 06; fax: (+33) 4 73 17 84 12. E-mail address: email@example.com (N. Macian).
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Received July 18, 2018
Received in revised form October 31, 2018
Accepted January 14, 2019