Renal effects of low dose methotrexate in rheumatoid arthritis.

OBJECTIVE: Methotrexate (MTX) treatment at high doses may cause renal failure. The effects of treatment with low MTX doses on kidney function are, however, unknown. The objective of our study was to investigate the effect of low MTX doses on kidney function. METHODS: The glomerular filtration rate was measured as the plasma clearance of 51Cr-EDTA and the clearance of 99mTc-dimercaptoacetyl-triglycine (correction of triglycerine) (99mTc-MAG3), a new renal tubular function agent, was used to measure tubular effects of MTX. RESULTS: Significant decrease of both 51Cr-EDTA clearance from 92 +/- 7 to 83 +/- 5 ml/min x 1.73 m2 (mean +/- SEM) and of the 99mTc-MAG3 clearance from 360 +/- 18 to 309 +/- 15 ml/min x 1.73 m2 (p < 0.05) was observed. CONCLUSION: Our results indicate that low dose MTX treatment (15 mg weekly) may significantly impair kidney function which has to be considered particularly in situations with combined treatment with other potentially nephrotoxic substances.