Methotrexate removal during haemodialysis in a patient with advanced laryngeal carcinoma

A 62-year-old patient on long-term haemodialysis who developed an inoperable T2N3Mo squamous-cell carcinoma of the larynx was treated with weekly low-dose methotrexate (MTX) after failing to respond to radiotherapy. The patient was initially given one dose of 10 mg MTX (6 mg/m2) as a 1-h infusion, then he received three further i.v. doses of 20 mg (12 mg/m2). Haemodialysis was performed 15-18 h after each dose and the patient received folinic acid (30 mg i.v.q 6 h) until the MTX concentration was < 0.1 mumol/l. The MTX concentration was measured regularly until it reached < 0.1 mumol/l, and additional samples were withdrawn pre- and post-dialysis. The MTX elimination rate constant and half-life were estimated with the patient on and off dialysis. The patient failed to respond to treatment but did not experience MTX-related toxicity. The elimination half-life ranged from 22 to 42 h when he was off dialysis but fell to a median of 5.5 h during dialysis. Low-dose MTX was given to a patient on regular haemodialysis without evidence of toxicity. The rate of MTX elimination was increased during haemodialysis, although high MTX concentrations persisted for several days and prolonged rescue with folinic acid was required.