The purpose of this study is to evaluate the analgesic effectiveness and safety of 37.5mg Tramadol hydrochloride/325mg Acetaminophen in the treatment of breakthrough pain in cancer patients.

The combination of tramadol HCI/acetaminophen provides a more rapid onset of action compared to tramadol HCI alone and a longer duration of action than acetaminophen alone. Therefore, the combination of tramadol and acetaminophen may be effective for the treatment of cancer pain as well as to allow lower cumulative daily dosages of each medication to be used.This is an open-label study. Patients will receive one-dose treatment of 37.5mg Tramadol/325mg Acetaminophen tablets.This study has been designed to investigate the following hypothesis:Tramadol hydrochloride/acetaminophen is effective in the treatment of breakthrough pain in cancer patients.The patients will complete basic questions on side effect at visits on entry, 10, 30 mins, and 1h.

The patients will receive only one dose treatment of Tramadol hydrochloride/Acetaminophen oral tablets throughout the study. The number of oral tablets be given will be depend on the total daily dose of around-clock medications. If around-clock medication is Tramadol <=400mg or codeine <=300mg or morphine <60mg, the breakthrough pain medication will be 1 tablet. If around-clock medication is morphine 60-120mg or Fentanyl >=25 ug/hr, the breakthrough pain medication will be 2 tablets.

Inclusion Criteria:

• Patients with a histologically, radiologically or haematologically confirmed malignancy whose pain is judged by the investigator to be caused by the malignancy
• Patients must have been on a stable daily dose of weak opioids or strong opioids for at least 72 hours prior to the start the study and must remain at the same dosage for the duration of the study
• Patients must have a VAS (Visual analog scale) >=40mm

Exclusion Criteria:

• Patients who have taken either morphine with daily dose more than 120mg or Fentanyl with daily dose more than 50ug/hr
• Patients with significant abnormalities in hepatic or renal function which would, in the opinion of the investigator, prevent the patients involvement in the study
• Patients with significant clinical abnormalities in CNS, respiratory or cardiovascular function, which in the investigators judgement prevents participation in the study
• Patients who have taken antidepressants or anti-epileptic drugs, sedative hypnotics, selective serotonin reuptake inhibitor, short-acting analgesics, topical medications and anesthetics and/or muscle relaxants when taking Tramadol/Acetaminophen