Oral administration of 5-fluorouracil: renal clearance and urinary concentration in man.

The pharmacokinetics of 5-fluouracil were studied in 9 patients with a history of bladder malignancies. A single dose of 250 mg. 5-fluorouracil was given orally and the renal clearance of active 5-fluorouracil was approximately 40 ml. per minute. The maximum serum (1,100 ng./ml. serum) and urinary concentrations (49,000 ng./ml. urine) of 5-fluorouracil occurred 20 and 40 minutes after administration, respectively. The urinary concentration per se is highly cytotoxic, whereas the short-lasting serum concentration previously has been proved to be without general cytotoxic effects even after continuous use of the drug for years. Although high concentrations of 5-fluorouracil are noted in the urine the antitumor effects of this treatment must be investigated further.