The Effect of Lacosamide in Peripheral Neuropathic Pain

Inclusion Criteria: 1. Age ≥ 18 years. 2. Probable or definite peripheral neuropathic pain for at least 3 months (Finnerup et al. 2016) 3. Average pain intensity of at least 4 and not above 9 on a 0-10 NRS during the 7-day baseline week (Dworkin et al. 2012). 4. Written informed consent. Exclusion Criteria: 1. Other causes of pain in the same area, or other concomitant pain that cannot be distinguished from the neuropathic pain 2. Patient who cannot cooperate or are unable to complete the project and patients who do not speak Danish. 3. Known and current cardiac conduction disturbance (2⁰ or 3⁰ atrioventricular (AV) block, prolonged QTc interval \> 450 ms, heart rate \<50 or \>110 bpm, a QRS interval \>120ms (ECG required)), significant cardiac, renal or liver disease or other severe illness. In patients treated with pregabalin also PQ interval \> 0,2s and cardiac disease. Sitting diastolic blood pressure below 50 mmHg or above 105 mmHg. 4. Major depressive episode within 6 months, recurrent depressive disorder or other significant psychiatric disease, alcohol, illicit drug or drug abuse. 5. Pregnancy or lactation 6. Woman of childbearing potential, unless they use and acceptable effective contraception measure as defined in the Clinical Trials Facilitation Group (CTFG) during the study and at least 2 weeks after, or if their male partner is vasectomized and their sole partners. Negative pregnancy test is required. 7. Known allergy to lacosamide or excipients. 8. Concomitant pain treatment with tricyclic antidepressants, topical analgesics (lidocaine, capsaicin), lamotrigine, oxcarbazepine, cannabinoids or strong opioids that cannot be discontinued. Other treatment for neuropathic pain are allowed in a stable dose (from 14 days before randomization to completion of the trial), if they cannot be tapered off completely. 9. Concomitant treatment with products known to be associated with PQ (PR) prolongation other than pregabalin. 10. Patients inappropriate for placebo 11. Planned surgery 12. Use of sodium channel blockers within at least five half-lives and investigational drugs within 30 days. 13. Patients on controlled sodium diet, unless the amount of sodium in the capsules is acceptable for their diet. 14. The score "yes" on item 4 or item 5 of the Suicidal Ideation section of the Columbia Suicide Severity Rating Scale (C-SSRS), if the ideation occurred in the past 6 months, or "yes on any item of the Suicidal Behaviour section, except for the "Non-suicidal Self Injurious Behaviour" if this behaviour occurred in the past 2 years.