High dose aspirin have been shown to increase the level of Methotrexat in patients with Rheumatoid Arthritis. However, most of RA patients are not currently treated with high dose aspirin. On the other hand, they frequently receive treatment with low dose aspirin. The effect of low dose aspirin on the levels of Methotrexate is not well known. Therefore,the purpose of this study is to assess the effect of low dose aspirin on the levels of methotrexate.

Thirty Rheumatoid Arthritis patients currently treated with low dose methotrexate (MTX) will participate in this study. On the day of intake of methotrexate, the patients will receive 10 mg of MTX. Serum levels of MTX will be measured at time 0,30 ,90, 120 minutes, and after 12 and 24 hours.

Two weeks later, the patients will be recommended to take 100 mg aspirin/d during a week. The levels of MTX will be measured after a week of treatment in a way similar to a week before.

Inclusion Criteria:

• RApatients treated with Methotrexate

Exclusion Criteria:

• Contraindication to aspirin