The incidence of pancytopenia in patients taking leflunomide alone or with methotrexate

Abstract

To estimate the incidence of pancytopenia in patients taking leflunomide with or without methotrexate in Australia. Review of spontaneous reports to the Australian Adverse Drug Reactions Advisory Committee (ADRAC); estimation of incidence using national prescription reimbursement data; concomitant exposure to methotrexate was estimated using three sources of information. ADRAC received 11 reports of pancytopenia (meeting predefined criteria) associated with the use of leflunomide during its first 31 months of marketing. In nine reports, the patients were also taking methotrexate. Estimates of incidence in patients taking leflunomide alone ranged from 1 in 3698 to 1 in 4582 patients exposed; for patients also taking methotrexate the estimates ranged from 1 in 575 to 1 in 822. Use of methotrexate with leflunomide increases the risk of pancytopenia compared with use of leflunomide alone. The haematological toxicity of the combination requires further study.