Folinic acid effect on 5-fluorouracil kinetics in vivo.

Synergy of folinic acid and FU has been shown in several experimental systems. In the present study we examined the kinetics of concurrent administration of folinic acid on the kinetics of FU in an in vivo model. Folinic acid significantly increased the amount of FU bound to the TS complex. In the sequential combination of MTX and FU folinic acid had no additional effect. The amount of FU incorporated into RNA was not affected in any of the treatment groups. The results indicate that folinic acid may improve FU cytotoxicity by increased FU binding to TS but has no additional effect on the synergistic sequential MTX-FU combination.