Folic acid supplementation during treatment of psoriasis with methotrexate: a randomized, double-blind, placebo-controlled trial

The value of folate supplementation in methotrexate (MTX)-treated patients remains controversial. To determine the effect of folic acid (FA) on the efficacy of MTX and the frequency of side-effects associated with MTX therapy. A 12-week double-blind clinical trial was conducted in patients with psoriasis stable on their long-term MTX doses but not receiving FA. They were randomized into two arms of either FA 5 mg or placebo daily. MTX doses were not changed throughout the study. Patients were monitored every 3 weeks by the same observer. Assessments included Psoriasis Area and Severity Index (PASI), a visual analogue scale (VAS) of patients' perception of their psoriasis severity and the Dermatology Life Quality Index (DLQI). Adverse events were systematically recorded. Haematological and biochemical monitoring was performed. Twenty-two patients with psoriasis were recruited. Age, sex and weekly MTX doses were similar in both groups. All 22 patients completed the study. The mean PASI in the FA group increased from 6.4 at baseline to 10.8 at 12 weeks. In the placebo group the mean PASI fell from 9.8 at baseline to 9.2 at 12 weeks. The mean change from baseline in the FA group was 4.4 vs. -0.6 in the placebo group (P < 0.05). Similar trends were observed in the changes in VAS and in the DLQI and differences between the groups were significant for both these parameters (P < 0.05). Few adverse effects were reported. This study suggests that supplementation with FA during long-term MTX treatment reduces the efficacy of MTX in the control of psoriasis. Due to the relatively small sample size and short duration of this study, no conclusions can be drawn regarding the possibility that FA may reduce the side-effects of MTX.