Irradiation of murine lip mucosa in combination with 5-fluorouracil, administered by single dose injection or continuous infusion.

The possible interaction of 5-fluorouracil (5-FU) and irradiation on mouse lip mucosa was studied, with special interest for the influence of the route of administration of the drug, either by single intraperitoneal (i.p.) injection or by 7 days continuous subcutaneous infusion. Apart from the possible modification by the drug of radiation-induced damage to the lip mucosa assessment was made of the systemic toxicity. No modification of the radiosensitivity of mouse lip mucosa nor of its repair capacity was observed with the use of 5-FU given either by i.p. injection or by continuous infusion. However, the combination of 5-FU and irradiation resulted in an increased systemic toxicity which was only seen when 5-FU was administered by an i.p. injection in close timing with irradiation. It is suggested that this increased systemic toxicity is caused by the combined effects of irradiation and 5-FU on the alimentary tract, although we could not demonstrate the mechanism of it.