This is an open-label (all people know the identity of the intervention), multi-center (study conducted at multiple sites), observational study (study in which the investigators/ physicians observe the patients and measure their outcomes). The study will enroll approximately 100 patients who will be taking prolonged release tapentadol hydrochloride with a dosing regimen stipulated in the product insert. As this is an observational study, assessment of patient will be based on the accepted clinical practice in the Philippines. Patients will be monitored at baseline (Day 1) and throughout the 84-day treatment period of prolonged release tapentadol hydrochloride (every 7 days for the first two weeks, and thereafter every 28 days for the next three months) for effectiveness with the help of short form Brief Pain Inventory (BPI) questionnaire. Safety evaluations will include assessment of adverse events, clinical laboratory tests, and co-morbid conditions. The total study will be conducted for 3 years and the duration of treatment will be for 84 days.