Influence of the administration of amifostine on the pharmacokinetics of 5-fluorouracil in patients with metastatic colorectal carcinoma

A high dose antineoplastic therapy with 5-fluorouracil (5-FU) is associated with severe side effects. It is thought that the cytoprotective drug amifostine can reduce these side effects when it is given prior to a chemotherapeutic course. In this study, the pharmacokinetic parameters of 5-FU are monitored in six patients, who received two chemotherapeutic courses of 2600 mg/m(2) BSA 5FU over 24 h, one course with 700 mg/m(2) BSA amifostine prior to the 5-FU infusion and the other without. 20 serum samples were drawn during each infusion time and the 5-FU concentrations were determined by a sensitive and selective GC-MS assay. The statistical analysis of the serum concentrations revealed no significant differences in the pharmacokinetic parameters of 5-FU, whether amifostine is administered or not. The conclusion can be drawn that a reduction of side effects is due to the cytoprotective effect of amifostine and not to a change in the serum concentrations of 5-FU.