Relationship between pharmacokinetics and therapeutic and adverse effects of methotrexate during the initial phase of treatment of moderate-severe and severe psoriasis
2006
Abstract
Psoriasis activity (the PASI score), folate concentrations in the plasma and red blood cells as well as plasma homocysteine were followed during the initial period of treatment of moderate-severe to severe psoriasis with low-dose oral methotrexate. Patients were randomized into two treatment arms: A (MTX week 1-16, MTX + folic acid week 17- 32) and B (MTX + folic acid week 1-16, MTX week 17- 32).
In the study arm A, the percent improvemet of PASI was lower than in the arm B (42%(SEM 10%) vs. 73% (SEM 7%), P<0.01). In the study arm B, however, the folate levels decreased and plasma homocysteine increased and more side effects were recorded.
Folic acid (20 mg/week) decreases therapeutic effect as well as side effects of methotrexate.