The rate of decrease in the disease activity of rheumatoid arthritis during treatment with adalimumab depends on the dose of methotrexate

Abstract

Objective The aim of this study was to analyze the efficacy of adalimumab (ADA) in patients with rheumatoid arthritis treated with or without methotrexate (MTX) and determine impact of the MTX dose. Methods Pearson’s product-moment correlation coefficient was used to assess the correlations between the improvement in the Disease Activity Score (DAS) 28- erythrocyte sedimentation rate (ESR) score and the MTX dose in patients receiving treatment with MTX at a dose of <8 mg/week, 8 mg/week and >8 mg/week. Patients ADA therapy was initiated in 68 rheumatoid arthritis patients between July 2008 and June 2013. The mean MTX dose was 9.6 ± 2.6 mg/week, and the patients were followed for 24 weeks. Results The mean DAS28-ESR scores at baseline and week 24 were 4.6 ± 1.3 and 2.7 ± 1.2 in the 60 patients treated with MTX and 4.5 ± 1.0 and 4.2 ± 1.5 in the eight patients treated without MTX, respectively. Clinical remission was achieved in 48% and 25% of the patients, respectively, by week 24. Moreover, 90.0% of the patients taking MTX continued to receive ADA until week 24, while 50.0% of the patients not taking MTX continued to receive ADA until week 24. Among the 35 patients receiving MTX at a dose of >8 mg/ week, the DAS28-ESR scores decreased rapidly from 4.4 ± 1.2 at baseline to 3.2 ± 1.1 at week 4 and further decreased to 2.4 ± 1.0 at week 24. Meanwhile, clinical remission was achieved in 57% of the patients receiving MTX at a dose of >8 mg/week and 36% of those receiving MTX at a dose of ≤8 mg/week. A significant correlation was noted between the improvement in the DAS-ESR score and the MTX dose. Conclusion In this study population, enhanced clinical efficacy of ADA was achieved in combination with the administration of a sufficient dose of MTX, determined to be >8 mg/week.