• The primary outcomes are analyses of adverse events (incidence, frequency,
  
• severity, attribution, adverse events causing withdrawal from study)
  

• The secondary outcomes are pain intensity (visual analog scale) assessment,
  
• patient global assessment of study medication, pain recall (least, worst and
  
• average pain); changes from baseline to each subsequent visit.
  

Immediate release (IR) tramadol has demonstrated efficacy in several pain conditions including: obstetrical, gynecological, orthopedic, abdominal, and oral surgery. The short elimination half-life of IR tramadol necessitates every 4-6 hour dosing to maintain optimum levels of analgesia in chronic pain. The study medication in this study is a once-daily, extended release (ER) tramadol formulation. This study is a multicenter, multiple-dose, 1-year open-label study designed to assess the safety and effectiveness of tramadol HCl ER. Patients with moderate to severe chronic non-malignant pain, requiring treatment with an analgesic on a daily basis, are eligible for study participation. Patients eligible for enrollment are as follows: those who completed 12 weeks in one of two prior double-blind studies ("roll-over patients") or those without participation in any prior study of tramadol HCl ER ("direct enrollment patients"). Following a screening evaluation and baseline assessment, roll-over patients will be treated for up to 38 weeks and direct enrollment patients for up to 58 weeks. At baseline (Visit 2), patients will receive tramadol HCl ER 100 mg once daily (QD) for 3 days; on day 4, they will increase to tramadol HCl ER 200 mg QD, based on tolerability. Patients will be required to be on a minimum dose of tramadol HCl ER 200 mg QD by Visit 3. At Visit 4, patients are required to begin treatment with a minimum dose of tramadol HCl ER 300 mg QD. The maximum dose of tramadol HCl ER for patients >= 75 years old is 300 mg QD. By Visit 5, patients < 75 years old are to be initiated on a tramadol HCl ER dose of 400 mg QD. Patients who cannot tolerate a dose increase of tramadol HCl ER from 300 mg or 400 mg QD (due to side effects) or who upon dose increase cannot tolerate the dose will be permitted to reduce the tramadol HCl ER dose to 300 mg QD. Patients unable to tolerate tramadol HCl ER 300 mg or 400 mg QD or those who had pain unresponsive to appropriate dose adjustments will be discontinued and alternate analgesic therapy initiated, as appropriate.