Pharmacokinetics of oral idarubicin in breast cancer patients with reference to antitumor activity and side effects.

The pharmacokinetics of orally administered idarubicin (22.5 mg/m2/week) and idarubicinol were studied for 12 weeks in 14 patients with breast cancer. Plasma concentrations were monitored for 72 hours after the first, fourth, and twelfth doses and trough concentrations after 1, 2, 3, 4, 5, 7, 11, and 12 weeks of treatment. The half-lives of idarubicin and idarubicinol were 19 and 60 hours, respectively. No time-dependent changes or cumulation were observed. The metabolic ratio showed little variation. The plasma AUCs of idarubicin and idarubicinol varied between patients but were fairly constant in individual patients. The sum of the plasma AUCs was lower in patients with rapid progression than in patients who responded to treatment. A correlation between this parameter and the relative decrease in the leukocyte counts was demonstrated (p less than 0.05). No correlation was found between the pharmacokinetic parameters and the time to final progression.