An Efficacy and Safety Study of Acetaminophen Plus Tramadol Hydrochloride (JNS013) in Participants With Chronic Pain

Fixed dose combination of tramadol 37.5 milligram (mg)/acetaminophen 325 mg, 1 or 2 tablets 4 times daily will be given for one week; dose level will be fixed for each participant during the second week based on analgesic efficacy and tolerability (maximum daily dose will be 8 tablets).

Fixed dose combination of tramadol 37.5 mg/acetaminophen 325 mg, 1 or 2 tablets (same dose \[number of tablets\] as that for the second week in the open-label period) will be given 4 times daily up to 4 weeks.

Matching placebo will be given up to 4 weeks.