The purpose of this study is to assess the effectiveness of ULTRACET® (a combination analgesic) as add-on therapy in rheumatoid arthritis patients taking an NSAID (e.g. Advil®, Motrin® or other nonsteroidal anti-inflammatory drug) or a COX-2 inhibitor (e.g. Celebrex®).

This is a randomized, multicenter, placebo-controlled, double-blind study to evaluate the efficacy and safety of ULTRACET® (tramadol 37.5 mg and acetaminophen 325 mg) as add-on therapy in rheumatoid arthritis patients taking an NSAID or a COX-2 inhibitor. The patients will be randomized into 2 treatment groups: The first group will receive one ULTRACET® tablet 3 times per day for 7 days. The second group will receive one placebo tablet 3 times per day for 7 days. The primary efficacy measurement will be the patients' average daily pain score. Safety will be monitored throughout the study. The study hypothesis is that ULTRACET® will be well tolerated and the average daily pain relief score for the ULTRACET® treatment group will be better than that of placebo group. Patients will take one ULTRACET® tablet or placebo by mouth 3 times per day, for 7 days.

Inclusion Criteria:

• Patients diagnosed with rheumatoid arthritis at least 6 months before the participation in the clinical trial, (defined by having more than 4 of the diagnosis criteria suggested by American College of Rheumatology (ACR
• 1987))
• have been on a stable daily dose of an NSAID or a COX-2 inhibitor for at least 30 days prior to the start of the study
• have arthralgia (arthritis pain in the joints) for at least 2 days before the entering clinical trial, with a pain score on the Visual Analogue Scale (VAS) of 40 mm or greater.

Exclusion Criteria:

• Have had an inadequate response to Tramadol HCl therapy, or have discontinued Tramadol HCl therapy due to adverse events
• have taken Tramadol HCl within 30 days prior to study entry
• have recently taken other medications for pain relief, (other than their daily NSAID or COX-2 inhibitor
• daily use of aspirin at a dose greater than 100 mg per day.