A Study Of Celecoxib Versus Diclofenac In Patients With Ankylosing Spondylitis

Inclusion Criteria: * Male or female, 18 to 75 years of age, inclusive. * Clinical diagnosis of ankylosing spondylitis: * Willing to stop existing NSAID/COX-2 inhibitor treatment for up to two weeks. * Having given written informed consent to participate in the trial. * Pain intensity ≥ 40 mm on the visual analog scale, worsening by at least 30 % compared to that recorded at the screening visit. * Last administration of analgesic without anti-inflammatory activity is ≥ 8 h, the last administration of long-acting NSAIDs is ≥ 72 h Exclusion Criteria: * Patients with acute peripheral articular disease (defined by the onset within 4 weeks prior to visit * Known inflammatory enteropathy (e.g. ulcerative colitis, Crohn's disease). * Ongoing extra-articular signs (e.g. cardiac involvement). * Current painful vertebral compression. * Requirement to start physiotherapy, re-education or manipulation * History of clinical gastroduodenal ulcer in the year preceding inclusion, confirmed by endoscopy; continuing gastro-intestinal bleeding. * Cardiac failure or known renal insufficiency that could be affected by study medication, chronic or acute hepatic insufficiency, significant coagulation disorders or history of asthma. * Current or history of malignancy (except: patients having a basal cell carcinoma or other malignancy operated on and in remission for 5 years before inclusion in the trial). * Pregnancy, women of childbearing potential not using adequate contraceptive methods or nursing mothers. * Subject who has evidence of alcohol or drug abuse. * Participation in any other clinical study within 30 days prior to the screening visit. * Any condition that would prevent the patient from entering the study, according to the investigator's judgment. * Known hypersensitivity to celecoxib, sulphonamides or any NSAID (including salicylic acid). * Taking the following medications: Muscle relaxants, hypnotic, anxiolytics, sedatives, tranquillizers or antidepressants (unless stable for 2 weeks before screening and continuing throughout the trial), NSAIDs or COX-2 inhibitors other than study medication, acetylsalicylic acid (ASA) \> 160 mg /day, anti-coagulants, ticlopidine, lithium, anti-TNF agents or methotrexate \> 15 mg/week (Note: ASA ≤ 160 mg/day for cardioprotection is permitted), Use of oral or systemic analgesic medication, except from paracetamol, within 3 days of study entry and through the study, Corticosteroids (PO/IM/IV/IA) in the 6 weeks preceding inclusion in the trial, Anti-ulcer medication including chronic (daily or almost daily) use of antacids \[Note: Occasional use of antacids during the study will be permitted.\] * Change in dose of a slow-acting drug (e.g. sulfasalazin, methotrexate) in the past 60 days preceding inclusion in the trial. * Taking paracetamol \> 2000 mg/day (including during the screening period).