Pharmacokinetics of ketoconazole in patients with neoplastic diseases.

Twenty-seven patients with advanced malignancies were given 200 mg of ketoconazole orally every 6 or 12 h. Blood samples were collected during these intervals and after the last dose to determine plasma concentrations and half-lives. The mean plasma concentrations measured after the initial dose were 1.7 +/- 1.1 microgram/ml at 2 h, 0.9 +/- 0.2 microgram/ml at 6 h, and 0.7 +/- 0.4 microgram/ml at 8 h. Plasma concentrations rose significantly in patients on the every-6-h schedule. Concentrations were more variable in patients on the every-12-h schedule, and changes in mean plasma concentrations after 7 and 14 days were not significant. Half-lives ranged from 1.3 to 11.6 h in individual patients. The mean half-life for all patients studied was 3.7 +/- 0.6 h on day 1. The calculated area under the curve was 12.0 +/- 4.7 micrograms-h/ml on day 1; it increased after 7 and 14 days of administration (every-6-h schedule), suggesting plasma binding or wide drug distribution or both. Saturation of storage compartments is also suggested. Less than 1% of the administered dose was recoverable as active drug from the urine over 6 h.