Drug switching patterns among patients with rheumatoid arthritis and osteoarthritis using COX‐2 specific inhibitors and non‐specific NSAIDs

PURPOSE: To compare RA and OA patients' time-to-switch after newly initiating treatment with three most commonly used non-specific (NS)-NSAIDs and two COX-2 inhibitors, celecoxib and rofecoxib. METHODS: Managed care enrollees newly prescribed celecoxib, rofecoxib, ibuprofen, naproxen or diclofenac were identified. Time to switch to a different NS-NSAID or COX-2 specific inhibitor was determined using time-to-event analysis and Cox proportional hazards models were used to estimate the odds ratio (OR) after controlling for potential confounders. RESULTS: The time to 25% of the cohort switching was longer for rofecoxib and celecoxib (159 and 205 days respectively) compared to the three NS-NSAIDs (49-78 days). Patients were at the highest risk of switching within the first 100 days of therapy. After adjusting for potential confounding factors, the OR for switching to another NS-NSAID or COX-2 specific inhibitor ranged from 1.74 to 2.35 for the three NS-NSAIDs compared to celecoxib (all comparisons, p < 0.01). Similar findings were obtained when comparing rofecoxib to each of the three NS-NSAIDS (all comparisons, p < 0.01). When COX-2 inhibitors combined were compared to NS-NSAIDS combined, the OR for switching was 1.53 (95% confidence interval = 1.42-1.65; p < 0.01) after adjusting for potential confounders. CONCLUSIONS: Patients on the COX-2 specific inhibitors (celecoxib and rofecoxib) were significantly less likely to switch their therapy than patients on NS-NSAIDS (ibuprofen, naproxen and diclofenac). These results suggest that COX-2 specific inhibitors may be a more effective treatment option when compared with NS-NSAIDs in usual clinical practice.