A multicentre, double-blind, randomised, placebo-controlled clinical trial to investigate pain relieving effects of the modified release (MR) formulation of flupirtine in patients suffering from moderate to severe chronic low back pain.

INTERVENTION: Product Name: Katadolon dual Pharmaceutical Form: Modified‐release tablet INN or Proposed INN: Flupirtine maleate Concentration unit: g gram(s) Concentration number: 0,400‐ Pharmaceutical form of the placebo: Tablet Route of administration of the placebo: Oral use CONDITION: chronic low back pain PRIMARY OUTCOME: Main Objective: The main objective of the study is to investigate the clinical efficacy of the pain relieving effects of the modified release formulation of flupirtine in a daily dosage of 400 and 800 mg as compared to placebo in patients suffering from moderate to severe chronic low back pain. Primary end point(s): The percentage of subjects with a meaningful relief of the overall low‐back pain intensity (defined either as at least 30% pain reduction assessed with an 11‐point Numerical Pain Rating Scale (NRS‐11), or as at least 2‐point reduction measured on the basis of a 5‐point Verbal Rating Scale (VRS‐5)) following treatment with flupirtine compared to placebo. Differences between Visit 4 and baseline (Visit 1) will be used for the primary endpoint assessments of this study. Secondary Objective: A secondary objective is to investigate the impact of the modified release formulation of flupirtine on pain sensitivity (pressure threshold) and tissue compliance of muscles in the affected back region compared with placebo.; Safety and tolerability of the MR formulation will be descriptively evaluated based on adverse events, vital signs and laboratory parameters.; INCLUSION CRITERIA: • Diagnosis: Moderate to severe chronic low back pain (3 – 12 months) at stage II – III as per “Mainzer Pain Staging System” (MPSS) according to GERBERSHAGEN • Back pain intensity rated as at least 5 on an 11‐point Numerical Pain Rating Scale (NRS‐11) and/or at least moderate on a 5‐Point Verbal Rating Scale (VRS‐5) before randomisation (at Visit 1) • Male or female patients, aged 18 to 75 • Women of childbearing potential must use a reliable method of contraception (e.g. implants, injectables, combined oral contraceptives, some IUDs, sexual abstinence or vasectomised partner) • The patient must give written informed consent, after having been informed about benefits and potential risks of the trial, as well as details of the insurance taken out to cover the subjects participating in the stud