Comparison of methotrexate with azathioprine or 6-mercaptopurine in refractory rheumatoid arthritis: a life-table analysis.

Methotrexate (MTX) appears to be useful in patients with rheumatoid arthritis (RA) refractory to other drugs but its long-term toxicity and efficacy are uncertain. A retrospective study of MTX in such patients in comparison with the purine analogues, azathioprine and 6-mercaptopurine was made using life-table analysis. Eighty-four patients took MTX in a median dose of 7.5 mg/week whilst 55 received purine analogues, 100 mg/day (median). By 12 months, 19.3% of patients had ceased MTX due to toxicity, compared with 29.3% for purine analogues. Toxicity severe enough to warrant stopping therapy was uncommon after 8 months with either drug. At 12 months 61.5% of the MTX patients had achieved defined criteria of improvement compared with 25.6% for the purine analogues (p less than 0.05). The number of patients improving on purine analogues did not increase substantially after 6 months, whereas the number improving with MTX continued to 12 months. MTX in a low-dose regimen is useful in refractory RA and superior to low-dose purine analogues.