[Blood cell concentration of methotrexate in long-term therapy of inflammatory rheumatic diseases]

To verify the possibility of a concomitant therapy control in 31 patients (18 psoriatic arthritis [PA], 13 rheumatoid arthritis [RA]) the blood cell concentration of Methotrexate (MTX) was continuously measured over a period of 6 months. The determinations were carried out by using a RIA of the CIS Corp. At any time MTX was determined laboratory and clinical examinations were done and the P-III-P serum-level was measured by using a RIA of the Behringwerke. The cellular MTX showed to be statistically significantly elevated compared to baseline, whereas within ranges of total cumulative dosages only insignificant fluctuations could be noticed. Like in the treatment of Psoriasis a strict correlation between the weekly administered dose and the cellular MTX could be established, the total cumulative dose, however, had no influence on the cellular MTX-level. In the treatment of RA slightly higher weekly dosages were necessary, which caused significantly higher cellular MTX concentrations in RA patients. Some correlations between clinical as well as serological parameters of disease activity could be noticed, nevertheless they do not allow distinct interpretations. In both diseases a significant relationship between the cellular MTX-level and the P-III-P serum-level could be realized. A storage of MTX in blood cells, especially in erythrocytes, seems to be evident. To reach therapeutical benefit in RA slightly higher mean dosages may be necessary. A therapy monitoring by the means of continuous determinations of cellular MTX seems to be impossible. In contrast an approach to the early detection of liver fibrosis can be given by the correlation between cellular MTX and the P-III-P serum levels.