Normally chronic tumor related pain is controlled when subjects receive repeated doses of opioid analgesics. However, opioid therapy is commonly associated with side effects such as nausea, vomiting, sedation, constipation, addiction, tolerance, and respiratory depression. Tapentadol, a newly synthesized drug with an Prolonged Release (ER) formulation, also acts as a centrally acting pain reliever but has a dual mode of action.