An anticancer drug that increases the effectiveness of fluorouracil. Also called ethynyluracil. OR An orally-active fluoropyrimidine analogue. Eniluracil inhibits dihydropyrimidine dehydrogenase, the rate-limiting enzyme that catabolizes and inactivates 5-fluorouracil (5-FU) in the liver. Co-administration of ethynyluracil permits the oral administration of 5-FU.