• Malin Erika Carmland, Melissa Dall Kreutzfeldt, Jakob Vormstrup Holbech, Peter Kolind Brask-Thomsen, Thomas Krøigård, Peter Nørregaard Hansen, Hatice Tankisi, Troels Staehelin Jensen, Flemming Winther Bach, Søren Hein Sindrup, and Nanna Brix Finnerup.
• Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark.
• Eur J Pain. 2024 Jan 1; 28 (1): 105119105-119.

BackgroundNeuropathic pain is common and difficult to treat. The sodium channel blocker lacosamide is efficacious in animal models of pain, but its effect on neuropathic pain in humans is inconclusive.MethodsIn a multicentre, randomized, double-blinded placebo-controlled phenotype stratified trial, we examined if lacosamide produced better pain relief in patients with the irritable nociceptor phenotype compared to those without. The primary outcome was the change in daily average pain from baseline to last week of 12 weeks of treatment. Secondary and tertiary outcomes included pain relief, patient global impression of change and presence of 30% and 50% pain reduction.ResultsThe study was prematurely closed with 93 patients included and 63 randomized to lacosamide or placebo in a 2:1 ratio, of which 49 fulfilled the per protocol criteria and was used for the primary objective. We did not find a better effect of lacosamide in patients with the irritable nociceptor phenotype, the 95% CI for the primary objective was 0.41 (-1.2 to 2.0). For all patients randomized, lacosamide had no effect on the primary outcome, but significantly more patients were responders to lacosamide than during placebo, with an NNT of 4.0 (95% CI 2.3-16.1) and 5.0 (95% CI 2.8-24.5) for 30% and 50% pain reduction respectively. We did not identify any predictors for response. Lacosamide was generally well tolerated.ConclusionWe could not confirm that lacosamide was more efficacious in patients with the irritable nociceptor type, but the study was prematurely closed, so we cannot exclude a small difference.SignificanceTreatment of neuropathic pain is often a trial and error process. Little is known about which patient benefit from which kind of medication. The sodium channel blocker lacosamide shows variable effect on neuropathic pain. Pain sensory phenotype, as defined by quantitative sensory testing, did not predict response to treatment with lacosamide.© 2023 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFIC ®.

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