Jl. Grem et al., Phase I and pharmacokinetic trial of weekly oral fluorouracil given with eniluracil and low-dose leucovorin to patients with solid tumors, J CL ONCOL, 18(23), 2000, pp. 3952-3963
Purpose: Fluorouracil (5-FU) given as a weekly, high-dose 24-hour infusion
is active and tolerable. We evaluated an oral regimen of eniluracil (which
inactivates dihydropyrimidine dehydrogenase [DPD]), 5-FU, and leucovorin ta
simulate this schedule.
Patients and Methods: Patients received a single 24-hour infusion of 5-FU (
2,300 mg/m(2) on day 2) with leucovorin(15 mg orally [PO] bid on days 1 thr
ough 3) to provide reference pharmacokinetic data. Two weeks later, patient
s began treatment with eniluracil (20 mg) and leucovorin (15 mg) (90 bid on
days 1 through 3) and 5-FU (10 to 15 mg/m2 PO bid on day 2).
Results: Dose-limiting toxicity (diarrhea, neutropenia, and fatigue) was se
en with 5-FU 15 mg/m2 PO bid on day 2 given weekly for either 6 of 8 weeks
or 3 of 4 weeks, whereas five of seven patients tolerated 5-FU 10 mg/m2 PO
bid given weekly for 3 of 4 weeks. Eniluracil led to a 35-fold reduction in
5-FU clearance. Fluoro-beta-alanine, a 5-FU catabolite, was not detected i
n plasma during oral 5-FU-eniluracil therapy. DPD activity was markedly sup
pressed in all patients during eniluracil therapy; the inactivation persist
ed after the last eniluracil dose; percentages of baseline values were 1.8%
on day 5, 4.5% on day 12, and 23.6% on day 19.
Conclusion: The recommended oral dosage of 5-FU (10 mg/m2 PO bid) given wit
h eniluracil and leucovorin is approximately 115-fold lower than the refere
nce dosage for 24-hour infusional 5-FU. This difference is greater than exp
ected given the reduction in 5-FU clearance. DPD inactivation persisted for
several weeks after completion of eniluracil therapy. (C) 2000 by American
Society of Clinical Oncology.