Risk of haematological events and preventive effect of folic acid in methotrexate users with chronic kidney disease and rheumatoid arthritis: Analysis of the Japanese Adverse Drug Event Report database.

Although methotrexate (MTX) for rheumatoid arthritis (RA) sometimes causes severe haematological toxicities in users with chronic kidney disease (CKD), data are limited regarding the risk of these events and the preventive effect of folic acid. This study evaluated the risk of haematological toxicities and the efficacy of folic acid in MTX users with CKD using the Japanese Adverse Drug Event Report. In total, 5,648 oral MTX users with RA were identified, including 630 with haematological toxicities. MTX users with CKD had significantly increased risk of haematological toxicities compared with those without CKD when folic acid was not used (OR 3.72; 95% CI 2.87-4.81; P < 0.01). Multivariate logistic analysis showed that the risk of haematological toxicities was significantly decreased by only folic acid (OR 0.16; 95% CI 0.04-0.62; P < 0.01). This result provides useful information for preventing severe haematological toxicities in MTX users with CKD and RA.