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The effect of organic acids on renal clearance of methotrexate in man
Author(s) -
Liegler Donald G.,
Henderson Edward S.,
Hahn Mary Anne,
Oliverio Vincent T.
Publication year - 1969
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1002/cpt1969106849
Subject(s) - methotrexate , renal function , probenecid , clearance , pharmacology , pah clearance , chemistry , inulin , medicine , endocrinology , renal blood flow , biochemistry , effective renal plasma flow , urology
The renal clearance of the folic acid antagonist, methotrexate, was compared with that of inulin and para‐aminohippurate in 15 patients with disseminated malignancy. The clearance of methotrexate exceeded that of inulin clearance in all cases, indicating methotrexate is not only filtered but is also actively secreted by the renal tubules. The simultaneous intravenous administration of weak organic acids resulted, generally, in suppressive effects on the clearance of methotrexate. Salicylate and high concentrations of para‐aminohippurate reduced methotrexate clearance well below the glomerular filtration rate; whereas, sulfisoxazole had only a minimal effect on total methotrexate clearance. The variations of plasma protein binding of methotrexate induced by these same drugs did not correlate with the direction or degree of methotrexate clearance. It is concluded from these studies that methotrexate is excreted by a combination of glomerular filtration and active tubular transport and that methotrexate clearance is not directly related to the level of free methotrexate presented to the kidneys. It is furthermore suggested that the alterations in plasma protein binding and renal clearance of methotrexate provoked by the simultaneous administration of other organic acids may be clinically exploitable in cancer chemotherapy.