Author(s): Twelves C, GlynneJones R, Cassidy J, Schller J, Goggin T
Capecitabine (Xeloda) is a rationally designed oral, tumor-selective fluoropyrimidine carbamate aimed at preferential conversion to 5-fluorouracil (5-FU) within the tumor. Because capecitabine is extensively metabolized by the liver, it is important to establish whether liver dysfunction altered the pharmacokinetics of capecitabine and its metabolites. This was investigated in 14 cancer patients with normal liver function and in 13 with mild to moderate disturbance of liver biochemistry due to liver metastases. They received a single oral dose of capecitabine (1255 mg capecitabine/m2) with serial blood and urine samples collected up to 72 h after administration. Concentrations of capecitabine and its metabolites were determined in plasma by high-performance liquid chromatography or liquid chromatography coupled to mass spectrometry and in urine by 19F-nuclear magnetic resonance spectroscopy. Although plasma concentrations of capecitabine, 5'-deoxy-5-fluorouridine, 5-FU, dihydro-5-FU, and alpha-fluoro-beta-alanine were, in general, higher in patients with liver dysfunction, the opposite was found for 5'-deoxy-5-fluorocytidine. These effects were not clinically significant. Total urinary recovery of capecitabine and its metabolites was 71% of the administered dose in patients with normal hepatic function and 77% in patients with hepatic impairment. The absolute bioavailability of 5'-deoxy-5-fluorouridine was estimated as 42% in patients with normal hepatic function and 62% in patients with impaired hepatic function. In summary, mild to moderate hepatic dysfunction had no clinically significant influence on the pharmacokinetic parameters of capecitabine and its metabolites. Although caution should be exercised when capecitabine is administered to patients with mildly to moderately impaired hepatic function, there is no need for, a priori, adjustment of the dose.