Objective: To compare the efficacy and safety of piroxicam 20 mg once a day for 14 or 28 days in patients with knee osteoarthritis (OA) and synovial effusion.
Methods: We conducted a multicenter, randomized, double blind study in 1905 outpatients. Efficacy was assessed by changes in synovial effusion, pain on a 100 mm visual analog scale (VAS), and impairment using Lequesne's functional index. Patients were classified at Day 28 as improved (defined as VAS and Lequesne index decrease of at least 30% from Day 14), worsened (defined as VAS and Lequesne index increase of at least 30% from Day 14), or unchanged. Safety was assessed on the basis of adverse events reported by the patients.
Results: After 14 days, changes in pain, synovial effusion, and functional impairment significantly decreased from baseline within each group (p < 0.001, respectively), but did not differ between the groups. Between 14 and 28 days, outcome measure changes were significantly better in the 28 day group, p = 0.01, 0.0001, and 0.0001, respectively. In the 28 day and 14 day groups, improvement with regard to pain was observed for 339 (52.4%) and 280 (29.4%) patients, respectively, (p < 0.0001), and with regard to functional impairment for 298 (31.5%) and 233 (24.3%) patients (p < 0.0001). Adverse events accounted for 7.5 and 6.7% of withdrawals in the 28 day and 14 day groups, respectively.
Conclusion: When administration of piroxicam 20 mg is prolonged to 28 days, continuing benefit is observed for some patients with knee OA with painful synovial effusion without a significant difference in safety.