Methotrexate-related toxicity in patients with rheumatoid arthritis and renal dysfunction

There are limited studies regarding the safety of methotrexate (MTX) in patients with reduced renal function. This study aimed to investigate methotrexate (MTX)-related toxicity in patients with rheumatoid arthritis (RA) and renal dysfunction. This retrospective cohort study included patients with RA and renal dysfunction. Renal dysfunction was defined as an estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m². We classified the patients into two groups according to the onset of renal dysfunction: newly and previously developed group. MTX-associated toxicity included renal toxicity, hepatotoxicity, serious infection, pancytopenia, leukopenia, thrombocytopenia and mucositis. Cox analysis was performed to determine the factors associated with toxicity. The study included 120 patients with RA and renal dysfunction receiving MTX (66: newly developed; 54: previously developed). The median eGFR was 52.1 mL/min/1.73 m² [IQR 47.1-57.3]. Thirty-five patients (29.2%) experienced toxicity, and the median time to toxicity events was 23 months (IQR 10-57). Toxicity was distributed as follows: leukopenia (10%, 12/120), renal toxicity (5.8%, 7/120), hepatotoxicity (7.5%, 9/120), serious infection (8.3%, 10/120), pancytopenia (5.0%, 6/120), thrombocytopenia (5.8%, 7/120), and mucositis (5.8%, 7/120). The toxicity rate did not differ significantly between newly and previously developed group [23/66 (34.8%) vs. 12/54 (22.2%), P = 0.130]. Multivariate analysis revealed that hydroxychloroquine use (HR 0.425, 95% CI 0.212-0.853, P = 0.016), baseline eGFR (HR 0.938, 95% CI 0.890-0.988, P = 0.015) and being female (HR 10.538, 95% CI 1.375-80.793, P = 0.023) were associated with MTX-related toxicity. Toxicity occurred in approximately 30% of patients with RA and renal dysfunction receiving MTX treatment. Hydroxychloroquine use exhibited a protective effect against MTX-associated toxicity development.