Side Effects of Methotrexate and Tumor Necrosis Factor Inhibitors: Differences in Tolerability Among Patients With Psoriatic Arthritis and Rheumatoid Arthritis

OBJECTIVE: To examine the prevalence of side effects with methotrexate (MTX) and tumor necrosis factor inhibitors (TNFi) among patients with psoriatic arthritis (PsA) and rheumatoid arthritis (RA). METHODS: This retrospective analysis, conducted between January 2000 and January 2019, used data from the FORWARD databank. Adult patients enrolled in the registry with self‐reported and physician‐confirmed diagnosis of PsA or RA were included if they had completed at least one questionnaire before initiating and within 12 months following initiation of MTX or a TNFi. The primary outcome was to examine the prevalence of side effects with MTX and TNFi within the year following treatment initiation. Multivariate logistic regression analysis was performed to examine the association between PsA and RA and the reporting of their side effects. RESULTS: Overall, 116 patients with PsA and 4247 patients with RA newly initiated MTX, and 124 patients with PsA and 4361 patients with RA newly initiated a TNFi. Patients with PsA were more likely to report MTX‐related side effects than those with RA (44.8% vs. 29.4%), whereas similar proportions of patients with PsA and RA reported TNFi‐related side effects within the first year (24.2% and 22.8%, respectively). Additionally, patients with PsA initiating MTX were more likely to report nausea, vomiting, abdominal pain, depression, and tinnitus than patients with RA initiating MTX or those with PsA or RA initiating a TNFi. CONCLUSION: Patients with PsA reported more side effects than patients with RA, and this difference was more pronounced in those receiving MTX versus TNFi.