Enhancement of antitumor activity of 5-fluorouracil by ribothymidine.

The antitumor activity of 5-fluorouracil (5-FU) in combination with ribothymidine was examined on some experimental murine carcinomas. The antitumor activity of 5-FU against Ehrlich ascites carcinoma was markedly enhanced by intraperitoneal coadministration of ribothymidine. The enhancement of the antitumor activity of 5-FU by ribothymidine was also observed against Ehrlich solid carcinoma both by oral and intraperitoneal administrations. Furthermore, the combination therapy of 5-FU and ribothymidine was effective even on 5-FU-resistant P388 leukemia. These results suggest that the combination of 5-FU and ribothymidine may be more effective than 5-FU monotherapy in clinical use.