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

The main objective of the study is to evaluate the effectiveness, safety, and tolerability of increasing doses of tapentadol prolonged release (PR) (500 mg per day) versus a combination of tapentadol PR (300 mg per day) and pregabalin (to 300 mg per day) in subjects requiring additional analgesia after titration to tapentadol PR 300 mg per day.

This is a clinical effectiveness trial designed to establish a link between anticipated clinical outcomes and the clinical practice by means of selected measures of clinical and subject reported outcomes. Since, severe low back pain with a neuropathic component, the targeted study population, is frequently treated with a combination therapy (monotherapy is often not effective enough) it is of interest to determine if tapentadol alone (combining 2 mechanisms of action in a single molecule) could be as effective as a combination of tapentadol plus pregabalin. Furthermore, the tolerability profiles of monotherapy versus combination are of interest.

Participants with a diagnosis of chronic low back pain (defined as pain lasting for at least 3 month) and requiring a strong analgesic (World Health Organization \[WHO\] Step III) as judged by the investigator and having a positive or unclear score using the painDETECT diagnostic screening questionnaire will enter the open-label titration tapentadol prolonged release (PR) period. In total participants will have 11 planned scheduled visits scheduled over 105 days. At the Enrollment Visit \[Day -14 (3 to 14 days prior to the Baseline Visit)\] the inclusion and exclusion criteria will be checked to evaluate the participant's eligibility for the trial. Participants on previous analgesics will start a washout period three days up to 2 weeks.The duration of the washout period will depend on previous opioid analgesics and co-analgesics and their respective doses, down-tapering steps. Participants who do not need a washout of previous analgesic treatment (e.g. WHO Step I analgesics), a baseline visit can be scheduled as soon as clinical laboratory monitoring results are available.

At the Baseline Visit (Day 1) participants will start the 3 week open-label titration period tapentadol prolonged release (PR) at doses of 2 x 50 mg per day and will be titrated upwards in steps of 100 mg (2 x 50 mg) on a weekly basis.

Participants who do not qualify for randomization may continue the trial in the open-label continuation arm if they have already reached a satisfactory level of pain relief.

Participants qualifying for randomization in the comparative period (Day 22 to 77) will be allocated to 1 of 2 treatment arms and will continue treatment.

Either they continue on tapentadol prolonged release (PR) with increasing doses of tapentadol PR

* After the randomization visit, participants will titrate up to a total daily dose of 400 mg.
* 1 week after the randomization visit, will titrate up to a total daily dose of 500 mg. Participants in this treatment arm will receive a final dose of 500 mg tapentadol PR per day.

Or start on a combination of tapentadol PR 300 mg per day with pregabalin

* After the randomization visit, participants will continue their previous regimen of tapentadol PR 2 x 150 mg per day plus pregabalin 2 x 75 mg (total daily dose of 150 mg pregabalin).
* 1 week after the randomization visit, participants will continue their previous regimen (end of titration period) of tapentadol PR 2 x 150 mg per day plus pregabalin 2 x 150 mg (total daily dose of 300 mg pregabalin). Participants in this treatment arm will receive a final dose of 300 mg tapentadol PR and 300 mg pregabalin.

Participants in the Comparative Period can be assigned to the open-label pick-up arm and will be treated with a stable dose of tapentadol PR 300 mg per day or 400 mg per day if they experience treatment emergent adverse events (at least possibly related to investigational medicinal product).The open-label pick-up period theoretically starts on Day 29, i.e. one week after the Randomization Visit.

The Final Evaluation (Day 77) is planned to take place 8 weeks after randomization.

After the Final Evaluation a Follow-up Period (blinded tapering down/out of IMP in Week 12 and Follow-up Visit (up to Day 91) will take place. Tapering down/out of medication will be performed according to the Summary of Product Characteristics.

Eligibility Criteria:
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.