The aim of the clinical study is to evaluate the Relationship to Efficacy of Treatment in Psoriatic Patients The aim of the clinical study is to evaluate the relationship between intracellular concentration of methotrexate (MTX), body exposition to the drug and clinical effect of low-dose methotrexate (LDMTX) therapy of psoriasis in a 3-month clinical study. 17 patients (4 men, 13 women) suffering from generalized or palmoplantar form of psoriasis were treated with MTX in the dose of 15 mg (group A, N = 11) or 7.5 mg (group B,N = 6) taken orally, once weekly. The study revealed marked interindividual variations of kinetic parameters were low. The steady state of MTX concentration in erythrocytes was obtained at the period of week 5 to 9. A statistically significant relationship was found between the body drug exposure [calculated as the area under the curve of methotrexate plasma concentration 24 hours after the first dose administration (AUCMTX)] and erythrocyte concentration of MTX at week 13 (rs = 0.93, p < 0.0001). The results showed statistically significant differences in concentration of MTX in erythrocytes between both groups at week 13 of treatment (p < 0.01, Mann-Whitney unpaired test). The response (evaluated according to the drop in PASI score) correlated significantly with erythrocyte concentration of MTX (rs = -0.69, p < 0.01). Intracellular (i.e. erythrocyte) concentration of methotrexate reflects the body exposition to the drug and therapeutic effect of LDMTX treatment.

        Key words: psoriasis - low dose methotrexate - erythrocyte concentration of methotrexate - PASI score