The aim of our work is to evaluate a clinical efficacy of low dose methotrexate therapy (LDMTX) in the treatment of psoriasis in relation to drug plasma concentrations. 17 patients (4 men and 13 women), suffering from palmoplantar and generalized form of psoriasis, participated in a 3-month study. Drug pharmacokinetic parameters were calculated in each patient after oral administration of 15 mg methotrexate (group A; 10 patients) or 7.5 mg MTX (group B; 7 patients). Significant interindividual variability of pharmacokinetic parameters was found among patients in both groups, suggesting for different exposition to drug for each participant even if equal dose was administered in each group. Total methotrexate clearance correlated with creatinine clearance. Statistically significant relationship was obtained between drug pharmacokinetic parameters, measured and calculated as area under the curve of plasma methotrexate concentration, and efficacy of the treatment, assessed as a change of PASI score in each patient. Coefficient of correlation between final PASI score and plasma methotrexate concentrations, measured in three months period after the initial dose of low-dose methotrexate was rs = -0,67 (p<0.005).

        Key words: psoriasis - low dose methotrexate - pharmacokinetics - pharmacodynamics