WHEN FLOXURIDINE IS GIVEN BY RAPID INTRA-ARTERIAL INJECTION IT IS APPARENTLY RAPIDLY CATABOLIZED TO 5-FLUOROURACIL. THUS, RAPID INJECTION OF FLOXURIDINE PRODUCES THE SAME TOXIC AND ANTIMETABOLIC EFFECTS AS DOES 5-FLUOROURACIL. THE PRIMARY EFFECT IS TO INTERFERE WITH THE SYNTHESIS OF DEOXYRIBONUCLEIC ACID (DNA) AND TO A LESSER EXTENT INHIBIT THE FORMATION OF RIBONUCLEIC ACID (RNA). HOWEVER, WHEN FLOXURIDINE IS GIVEN BY CONTINUOUS INTRAARTERIAL INFUSION ITS DIRECT ANABOLISM TO FLOXURIDINE-MONOPHOSPHATE IS ENHANCED, THUS INCREASING THE INHIBITION OF DNA.