An Open-label Extension Study With Flexible Dosing of Extended-release (ER) Tapentadol (CG5503) to Treat Patients With Moderate to Severe Chronic Pain

All patients who complete the Phase 3 pivotal trials in osteoarthritis (R331333-PAI-3008; KF5503/11) and low back pain (R331333-PAI-3011; KF5503/23) and the Phase 3 safety trial in the non-European sites (R331333-PAI-3007; KF5503/24) will be allowed to continue participation in the program by entering this trial. The trial will consist of three periods (screening, open-label treatment period, and follow-up). In the open-label treatment/maintenance period (1 year), those patients in the safety trial R331333-PAI-3007 (KF5503/24) taking open-label Tapentadol (CG5503) extended release (ER) will continue the dosage they were taking without undergoing titration. All other patients will be titrated to the minimum therapeutic dosage of Tapentadol (CG5503) extended release (ER) over 1 week. The lowest therapeutic dose allowed in the study is 100 mg twice daily, and the maximum upper dosage of Tapentadol (CG5503) extended release (ER) base is 250 mg twice daily. Downward titration (not below the minimum therapeutic dose of 100 mg twice daily) is permitted at any time using the same decrements without any time restriction. Dosages will be assessed at the scheduled (and unscheduled, if any) visits and adjustment under investigator supervision will be made as necessary. Dosage adjustments should be kept to a minimum. Intake of paracetamol/acetaminophen two 500 mg tablets daily is permitted during the titration week, and during the remainder of the open-label treatment/maintenance period up to a maximum of 7 consecutive days but no more than 14 out of 30 days. Following Week 4, all visits will be scheduled at 4-week intervals, through Week 52. The end-of-treatment visit at Week 52 will include both safety and efficacy assessments. Patients will return to the site for a follow-up visit approximately 4 days after their last dose of Tapentadol (CG5503) extended release (ER) for final safety evaluations and completion of the opioid withdrawal assessments (clinical opioid withdrawal scale, or COWS, and subjective opioid withdrawal scale, or SOWS). Patients experiencing withdrawal symptoms prior to the follow-up visit may telephone and request to be seen sooner. Additionally, the research staff at the site will telephone subjects approximately 10 to 14 days after the last dose of Tapentadol (CG5503) extended release (ER) to inquire if any adverse events have occurred since the previous visit. Tapentadol (CG5503) extended release (ER): 50, 100, 150, 200, and 250 mg orally, taken twice daily (morning and evening) for a maximum duration of 1 year.