The LCAT study

INTERVENTION: Patients are treated with a placebo or Tapentadol for 3 months. CONDITION: Low back pain (LBP) ; ; PRIMARY OUTCOME: ‐ Conditioned Pain Modulation (CPM); ; ‐ Temporal summation (TS); ; ‐ Offset Analgesia (OA); ; ‐ Pain relief SECONDARY OUTCOME: ‐ Pain Detect questionnaire ; ; ‐ The Big Five Inventory ; ; ‐ Profile Of Mood States ; ; ‐ Neuropathic Pain Symptoms Inventory Questionnaire ; ; ‐ Hospital Anxiety and Depression Scale (HADS) ; ; ‐ C‐fiber density in the cornea INCLUSION CRITERIA: American Society of Anesthesiologists class 1 and 2 patients, 18 – 75 years; BMI < 40 kg/m2, and ability to give informed consent. Chronic Low Back Pain for > 3‐months with a pain score of 5 or more on a numerical rating scale ranging from 0 (= no pain) to 10 (= most extreme pain imaginable). To be enrolled in the study, patients need to have an absent/inactive CPM response.