[Methotrexate. Pharmacology applied to the treatment of rheumatoid arthritis].

Methotrexate (MTX) is used increasingly for the treatment of rheumatoid arthritis (RA). It is an antagonist of folic acid. For the low doses used in RA (less than 15 mg/week), MTX is completely and rapidly absorbed with an active process membrane transport. The frequent toxic effects of this drug (hepatotoxicity, hematologic or possible long-term oncogenicity) limit its widespread use. MTX is as effective in treating RA as the other second line drugs and always more rapidly effective, perhaps because of anti-inflammatory properties. MTX must at the present time be used only in severe RA, refractory to more than one classical slow acting drug. Despite this, it is an extremely promising new agent in the therapy of rheumatic diseases.