Dose Versus pharmacokinetics for predicting tolerance to 5‐day continuous infusion of 5‐FU

This non‐randomized study reports pharmaco‐clinical data on 5‐FU administered by the widely used 5‐day continuous infusion schedule to 42 patients with metastatic colorectal cancer; 5‐FU was given by hepatic intra‐arterial route (h.i.a.) at doses ranging from 800 to 1,450 mg/m2, and by a systemic intravenous route (i.v.) at doses ranging from 650 to 1,300 mg/m2. 5‐FU blood levels were available for a total of 179 cycles. Toxicity was dose‐de pendent during h.i.a. cycles but not during i.v. cycles. For h.i.a. cycles, 1,000 mg/m2/day represented the threshold dose for tolerance. The individual total cycle drug concentration‐time product might predict toxicity for both i.v. and h.i.a. cycle when the threshold is set at 30,000 ng/ml hr. These data may be of practical value for improving the therapeutic index of 5‐day continuous treatment by 5‐FU given by i.v. or h.i.a. routes.