Journal of Veterinary Medical Science
Online ISSN : 1347-7439
Print ISSN : 0916-7250
ISSN-L : 0916-7250
Potentiated Decrease of Plasma Folate Levels Caused by the Coadministration of Folic Acid in Rats Treated with Methotrexate
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1998 Volume 60 Issue 4 Pages 503-507


The decrease of plasma 5-methyltetrahydrofolic acid (5-MF) levels, postulated as an indicator of folate status, was studied following the administration of both methotrexate (MTX) alone and MTX with folic acid (FA) using rats as our experimental model. Blood and urine samples were serially collected over a 9 hr period after the administration of MTX, MTX with FA and from a control group to examine the plasma kinetics and the renal clearance of 5-MF. The pharmacokinetics of MTX and the plasma protein binding of 5-MF were also examined. The concentrations of these analytes were assayed using high performance liquid chromatography (HPLC). MTX administration produced decreased plasma 5-MF levels. This observed decrease was potentiated by oral FA administration, suggesting that the folate status was more severely altered by the coadministration of FA. The renal clearance of 5-MF also increased dose-dependently with FA (0.05-5 mg/kg) coadministration. The plasma protein binding of 5-MF was not affected by the FA administration, which indicates that the fraction of 5-MF that was filtered through the glomerular apparatus appeared to be unchanged. In addition, the pharmacokinetic profiles of MTX also appeared not to be affected by the addition of FA. We conclude that the inhibition of reabsorption of 5-MF in the renal tube by concurrent administration of MTX and FA must be one of the causal factors for the demonstrated decrease in the plasma 5-MF levels in rats.

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この記事はクリエイティブ・コモンズ [表示 - 非営利 - 改変禁止 4.0 国際]ライセンスの下に提供されています。
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