Comparative pharmacokinetics of doxorubicin and epirubicin in patients with gastrointestinal cancer.

The levels of doxorubicin (DOX) and epirubicin (epi-DOX) in serum, tumors, and normal tissues were assayed by high-performance liquid chromatography after peroperative administration of test doses (10 mg) to 14 patients with gastrointestinal cancer. Large interindividual variations were found. The drug levels also varied markedly between tissues from the same patient, with normal liver consistently having the highest drug concentration, followed by tumors and striated muscle, which had similar levels. In serum, a rapid initial distribution phase, with a half-life of about 5 minutes for DOX and 4 minutes for epi-DOX, was followed by a slower decrease in the drug levels. The concentration versus time curves were not influenced by the presence of liver metastases. No metabolites of DOX or epi-DOX were found during the time period studied, in most cases 2 hours after drug administration. Our pharmacokinetic results give no explanation for the claimed superiority of epi-DOX in the treatment of gastrointestinal cancer.