Pharmacokinetics of 5-methyltetrahydrofolate.

The pharmacokinetic behavior of the reduced folate coenzyme, 5-methyltetrahydrofolate, was studied in the rat. Following oral administration the coenzyme was well absorbed from the intestinal tract and was bound to serum proteins. Plasma disappearance occurred in two exponential phases with a t1/2 alpha of 23.5 min and t1/2 beta of 8.5 hr. 5-Methyltetrahydrofolate appeared to be readily taken up by the tissues and was excreted in the urine primarily in the initial 4-8 hr. with minimal degradation in the process.