Comparative pharmacokinetics and metabolism of doxorubicin and epirubicin in patients with metastatic breast cancer.

Abstract

We have studied the metabolism and pharmacokinetics of epirubicin (4'-epidoxorubicin), as compared to those of doxorubicin, in a total of 16 patients with metastatic breast cancer. Epirubicin metabolism markedly differs from that of doxorubicin, in that large amounts of glucuronides of epirubicinol and epirubicin were observed in plasma as well as in urine samples. The total plasma clearance of epirubicin was significantly higher than that of doxorubicin; this was interpreted as due to an increase of the distribution volume of epirubicin, since the terminal plasma half-lives of both drugs were similar. No significant modifications were observed in patients with hepatic metastases. The differences in the pharmacokinetic and metabolic properties of the two drugs may be responsible for the differences in toxicity that have been noticed between them in previous phase I and II studies.