Reducing the risk of methotrexate pneumonitis in rheumatoid arthritis.

Methotrexate (MTX) is the most commonly used diseasemodifying drug (DMARD) in rheumatoid arthritis (RA) [1]. It is a main anchor drug in many combination regimes with conventional DMARDs and biological agents. It has the longest drugsurvival time and a good benefit/toxicity ratio [2, 3]. However, toxicity is a major reason for MTX withdrawal in RA [3]. Pneumonitis is the reason for withdrawal of MTX in 1 in 108 patient-years compared with 1 in 35 patient-years for hepatic toxicity and 1 in 58 patient-years for neutropenia [3]. There are guidelines for effective monitoring of the hepatic and haematological toxicity of MTX [4, 5]. Pneumonitis following MTX is a potentially fatal hypersensitivity reaction and is far less predictable than hepatic and haematological toxicity. Current guidelines [4, 5] advise a pretreatment chest radiograph (CXR), though there are wide variations in clinical practice in screening for lung disease prior to commencing MTX for RA. This is due to conflicting views as to whether pre-existing pulmonary disease increases the risk of MTX pneumonitis. Many studies [6–11] suggest that pre-existing lung disease in RA increases the risk of pneumonitis. Not all studies [12, 13] have supported this view. We discuss the evidence for predicting MTX pneumonitis in RA and the usefulness of screening for lung disease in patients with RA prior to treatment with MTX.