Evaluation of Effectiveness and Tolerability of Tapentadol Hydrochloride in Subjects With Severe Chronic Low Back Pain Taking Either WHO Step I or Step II Analgesics or no Regular Analgesics

Inclusion Criteria: * Participants must have signed an Informed Consent Form. * Participants were men or non-pregnant, non-lactating women. Female participants must be postmenopausal, surgically sterile, or practicing an effective method of birth control. Women of childbearing potential must have a negative pregnancy test at screening. * Participants must be appropriately communicative to verbalize and to differentiate with regard to location and intensity of the pain. * Participants must be at least 18 years of age. * Participants must have a diagnosis of chronic low back pain; chronic pain defined as pain lasting for at least 3 months. * If the participant has radicular pain, this must have been present for at least 3 months and stable for the 4 weeks before enrollment. * Participants's pain must require a strong analgesic (defined as WHO Step III) as judged by the Investigator. * Participants must report a rate of satisfaction with their previous analgesic regimen not exceeding "fair" on a subject satisfaction with treatment scale (5-point VRS). * If under regular, daily pretreatment: * Participants must be taking a WHO Step I or Step II analgesic medication on a daily basis for at least 2 weeks prior to the Screening Visit. * The Investigator considers dose increase of WHO Step I analgesics (as mono- or combination therapy) and/or continuation with or dose increase of WHO Step II analgesics inadequate for the individual participant, whatever applicable. * Participants must have an average pain intensity score (NRS 3) greater than 5 points during the last 3 days prior to the Screening Visit. or * If no regular analgesic pretreatment is reported: * Participants must have an average pain intensity score (NRS-3) greater than 6 points in the last 3 days prior to the Screening Visit and related to low back pain. Exclusion Criteria: * Presence of a clinically significant disease or laboratory findings that in the Investigator's opinion may affect efficacy or safety assessments. * Presence of active systemic or local infection that may, in the opinion of the Investigator, affect the efficacy, quality of life/function or safety assessments. * History of alcohol or drug abuse, or suspicion of in Investigator's judgement. * Presence of concomitant autoimmune inflammatory conditions. * Known history of or laboratory values reflecting severe renal impairment. * Known history of moderately or severely impaired hepatic function. * History of or active hepatitis B or …