Discontinuation rate of sulfasalazine, leflunomide and methotrexate due to adverse events in a real-life setting (NOR-DMARD)

OBJECTIVES: MTX, LEF and SSZ are conventional synthetic DMARDs (csDMARDs) with a well-established role in the treatment of RA. We aimed to estimate and compare the relative risks for adverse events (AEs) and the discontinuation of these drugs owing to AEs. METHODS: We included all 3339 patients from the NOR-DMARD study treated with MTX, LEF or SSZ in monotherapy. All reported AEs were compared between treatment groups using quasi-Poisson regression. In addition, drug retention rates were analysed using Kaplan–Meier estimates with Cox regression to control for possible confounders. We analysed drug retention rates and cumulative risk of discontinuation attributable to AEs using the Kaplan–Meier estimator. We assessed age, sex, baseline DAS in 28 joints with ESR (DAS28-ESR), seropositivity, prednisolone use, previous DMARD use, year of inclusion and co-morbidity as possible cofounders. RESULTS: We found that the discontinuation rate attributable to AEs was significantly higher for LEF and SSZ than for MTX. After the first year, it was 13.7% (95% CI 12.2, 15.2), 39.6% (95% CI 34.8, 44) and 43.4% (95% CI 38.2, 48.1) for MTX, SSZ and LEF, respectively. Similar results were found when adjusting for confounders. The overall AEs were comparable across the treatment groups. The AE profile was as expected for each drug. CONCLUSION: Our work has shown a similar AE profile of csDMARDs to previous data. However, higher discontinuation rates for SSZ and LEF cannot be explained easily from AE profiles.