• Compare the effectiveness of Ultracet and Diclofenac based on the mean change of VAS pain score at baseline, week 2, 4, and 8
  

• Compare the Bath AS Functional Index (BASFI) and Bath AS Disease Activity Index (BASDAI) and its independent components. Evaluate the quality of life by SF-36 and its components and Safety endpoint(s) at baseline, week 2, 4, and 8.
  

This study is a single center, open labeled, randomized, parallel group trial to compare the effectiveness (pain relief) and safety of tramadol 37.5 mg and acetaminophen 325 mg (Ultracet) with Diclofenac in patients with ankylosing spondylitis receiving stable treatment of disease modifying anti-rheumatic drugs (DMARDs). Patients who meet the entry criteria will be randomized to one of the two treatment groups (Ultracet and Diclofenac). One group will treated with Tramadol 37.5 mg/Acetaminophen 325 mg combination tablet and another group will treated with Diclofenac 50 mg tablet. Patients randomized into this study will be intructed take the one tablet Ultracet or Diclofenac 50 mg by mouth twice a day for 8 weeks. Evaluations will be performed as outlined: at screening, at baseline, and at weeks 2, 4, and 8. Non-steroidal anti-inflammatory drugs (NSAID) therapy with drugs such as ndomethacin or more recently COX-2 inhibitors, are used to control the inflammation and pain in patients with ankylosing spondylitis. However, long-term usage of NSAIDs, including COX-2 inhibitors, are known to have gastrointestinal and possible cardiovascular toxic effects, which could restrict their use. Tramadol is a centrally acting analgesic compound. Acetaminophen is another centrally acting analgesic. The primary endpoint is to compare the mean change from baseline in VAS pain score between the two treatment groups (Ultracet vs Diclofenac). Other endpoints include (1) to compare the Bath AS Functional Index (BASFI) and its independent components, (2) to compare the Bath AS Disease Activity Index (BASDAI) and its independent components, and (3) to evaluate the quality of life by SF-36 and its components. The safety of Ultracet and Diclofenac in this patient population by analyzing safety data in terms of adverse events and laboratory values.

Experimental Group will treated with Ultracet (Tramadol 37.5 mg/Acetaminophen 325 mg combination tablet). Control Group will treated with Diclofenac 50 mg tablet. Patients randomized into this study will be intructed take the one tablet Ultracet or Diclofenac 50 mg twice a day for 8 weeks.