Low dose oral administration of 4-demethoxydaunorubicin (idarubicin) in advanced cancer patients. A pharmacokinetic study.

Data relating to 4-demethoxydaunorubicin (DMDR) pharmacokinetics after oral administration (10-15 mg/m2 per day for 3 days) were collected in a total of 12 patients with advanced breast cancer and melanoma. Drug absorption took place in the first 2-4 h after administration. Plasma levels of the reduced metabolite DMDRol were higher than those of the parent compound: Peak levels were 4-10 ng/ml for DMDR and 15-40 ng/ml for DMDRol. The dose-corrected area under the time-concentration curve (AUC) was consequently higher for DMDRol (12.3-74.7, mean 32.6 vs 2.4-7.4, mean 4.6 ng/ml.mg for DMDR). Apparent plasma terminal half-lives after the last dose administered were in the range of 13-36 (mean 23.7) h for DMDR and 30-81 (mean 58.9) h for DMDRol. Drug and the reduced metabolite accumulated in the blood cells; the ratio of AUC (blood) to AUC (plasma) was 1.40-3.75 (mean 2.80) for DMDR and 1.29-3.50 (mean 2.16) for DMDRol. The biliary excretion of the drug and of the fluorescent metabolites was studied in two additional patients with extrahepatic obstruction and percutaneous biliary drainage. In the first 7 days of therapy, biliary excretion (DMDR + DMDRol) accounted for 3.7%-4% of the administered dose. In contrast to our observations with doxorubicin and epirubicin, urinary excretion seems very likely to be more important for this drug than biliary excretion. In these patients urinary excretions were 2.2, 2.9 times (for DMDR) and 1.2, 3.4 times (for DMDRol) the biliary excretion.