Methotrexate (MTX) 為一葉酸拮抗劑。低劑量使用是安全且耐受性佳，目前作為治療類風濕性關節炎的長期治療藥物。全血球減少症在低劑量的MTX 是罕見的藥物不良反應。本文案例為62 歲患有類風濕性關節炎、充血性心臟衰竭、慢性腎臟疾病的女性，長期使用MTX 治療，增加每週治療劑量數個月後出現感染、全血球減少症。依據文獻查證，MTX 導致全血球減少症與劑量依賴有相關性。藉由文獻回顧，探討低劑量的MTX 引起全血球減少症的病因、危險因子、預防及治療方法，以提升用藥安全性。
 

Methotrexate (MTX) is a folate analogue. Low-dose MTX is safe and well tolerated,it is now first- line therapy for the treatment of rheumatoid arthritis. Pancytopenia is an uncommon adverse drug reaction of low-dose pulse MTX therapy.
This case is a 62-year-old woman with rheumatoid arthritis, congestive heart failure, chronic kidney disease. She had been treated with MTX for long- term. A few months before admission, she had increased treatment dosing, and appeared infection and pancytopenia. According to the literature review, MTX induced pancytipenia was considered dose - dependent. We discussed the pathogenesis, associated risk factor,prevent and treatment for MTX induced pancytopenia by literature review, hope to enhance drug safety.