AB1395 Switching from adalimumab to other disease-modifying antirheumatic drugs without apparent medical reasons in rheumatoid arthritis: Impact on health care service use

Background Patients with rheumatoid arthritis (RA) stabilized on adalimumab (ADA) might be incentivized to switch from ADA to a different therapy with a lesser copayment even without apparent intolerance or lack of efficacy with ADA treatment. Objectives To assess the impact of switching for no apparent medical reasons on health care service use in patients with RA stabilized on ADA therapy in a real-world setting. Methods Adults with ≥2 RA diagnoses and ≥90 days of continuous ADA use were identified from the Thomson Reuters MarketScan® database (2003–2010). Patients who subsequently switched from ADA to a different disease-modifying antirheumatic drug (DMARD) with a ≥5% copayment decrease were defined as nonmedical switchers, with the fill date for the switched-to DMARD as the index date. The index fill date was required to be within 90 days after the last ADA prescription, and there had to be no other fills in the prior 6 months. Patients who subsequently refilled a prescription for ADA within 90 days were defined as maintainers, with the refill date as the index date. No direct measure of disease activity or ADA intolerance is available in the claims data. Therefore, in order to identify patients who apparently tolerated ADA therapy and had disease control, both cohorts were required to have no hospitalizations, emergency department visits, or use of oral/injectable corticosteroids in the 6 months before the index date. Data analyses were performed for the 6-month period after the index date. Use of health care services and rates of treatment discontinuation (ie, ≥90-day gap in prescription fills) were compared between nonmedical switchers and maintainers using multivariate Poisson and Cox proportional-hazards multivariate regression models, respectively, adjusting for demographics, health care resource use and costs, and comorbidities identified in the 6-month period before the index date. Results A total of 6270 patients were identified as maintainers and 342 as nonmedical switchers. Of the 342 nonmedical switchers, 176 (51%) switched to another TNF antagonist and 166 (49%) switched to nonbiologic DMARDs. On average, nonmedical switchers decreased their monthly copayments by $36.2 or $43.9 if they switched to a nonbiologic DMARD or another TNF antagonist, respectively. Compared with maintainers, nonmedical switchers incurred 42% more emergency department visits (incidence rate ratio [IRR]=1.42, 95% confidence interval [CI]=1.07–1.88; P=.015) and 12% m