Comparison of Increasing Doses of Tapentadol Versus a Combination of Tapentadol and Pregabalin

Inclusion Criteria: * Subjects must have a diagnosis of chronic low back pain; chronic pain defined as pain lasting for at least 3 months. * Subject's pain must require a strong analgesic (defined as World Health Organization (WHO) step III) as judged by the investigator. * The painDETECT diagnostic screening questionnaire score must be: * "positive" or * "unclear".or If the subject is being treated with a stable regimen of centrally acting analgesics (opioids) and/or co-analgesics, even a "negative" painDETECT score (but of at least 9) at the enrollment visit will be acceptable. * If under regular daily pretreatment with a WHO step II/step III opioid analgesic and/or a centrally acting co-analgesic: * Subjects must be taking a WHO step II or step III analgesic or co- analgesic on a daily basis for at least 2 weeks prior to the enrollment visit. * Subjects pretreated with a WHO step II opioid analgesic and/or a centrally acting co-analgesic must have reported an average pain intensity score of at least 5 points (NRS-3≥5) during the last 3 days prior to the enrollment visit. or If under regular, daily pretreatment with a WHO step I analgesic monotherapy or if no regular analgesic pretreatment is reported: * Subjects must have an average pain intensity score of at least 6 points NRS-3≥6) in the last 3 days prior to the enrollment visit. Exclusion Criteria: * Presence of concomitant painful conditions other than low back pain that could confound the subject's trial assessments or self-evaluation of the index pain, e.g., syndromes with widespread pain such as fibromyalgia. * Low back pain caused by cancer and/or metastatic diseases. * Any painful procedures planned during the trial period (e.g., major surgery) that may, in the opinion of the investigator, affect the effectiveness or safety assessments of the Investigational Medicinal Product (IMP). * Pending litigation or application for insurance/governmental benefits due to chronic pain or disability and, if granted, benefits might be influenced by a successful participation in the trial. * Rare hereditary problems of galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption, lactose intolerance.