The administration of 5-fluorouracil by mouth

When 5-fluorouracil was administered by mouth, concentrations of the drug in blood and urine were comparable to and more sustained than those achieved after parenteral treatment in four of seven subjects. This finding serves as evidence that the same precautions against drug side effects are indicated with oral as with parenteral treatment. Patients with metastases to the bowel or congestive heart failure had poorer absorption of 5-fluorouracil. The findings are evidence that intravenous and oral administration of the drug can result in different levels of 5-fluorouracil in blood. It may be worthwhile evaluating the relationship among blood levels, different patterns of absorption, and therapeutic response as a means of determining the optimal mode of therapy. One patient who failed to respond to intravenous 5-fluorouracil responded to oral 5-fluorouracil. Objective regression of hepatic and other metastases were observed in four patients treated with 5-fluorouracil by mouth.