To explore whether the duration of prior low-dose methotrexate treatment (MTX; ≤8 mg/week) influences the safety and effectiveness of high-dose MTX (>8 mg/week) in Japanese patients with rheumatoid arthritis (RA).
This post hoc sub-analysis of a Japanese post-marketing surveillance study evaluated patients initiating high-dose MTX with ≥1 year or <1 year prior low-dose MTX use. Over 24 or 52 weeks, adverse drug reactions (ADRs) were monitored, and effectiveness was assessed using the Disease Activity Score in 28 joints, erythrocyte sedimentation rate [DAS28-4 (ESR)].
One thousand two hundred and ninety-two MTX ≥1 year and 1001 MTX <1 year patients were included. The incidence of ADRs during the 24- and 52-week follow-up period was significantly more frequent in MTX <1 year than ≥1 year patients and serious ADRs were significantly higher in MTX <1 year than ≥1 year patients during the 52-week follow-up period (all 
High-dose MTX reduced disease activity regardless of prior treatment duration, but ADRs occurred more frequently among MTX <1 year patients compared to MTX ≥1 year patients.