Pharmacokinetics of guanazole in patients with acute myelocytic leukemia

Levels of guanazole (GZ) in plasma and packed cells were determined after a single tracer dose of 14C-guanazole or during a 5-day continuous intravenous therapeutic infusion of unlabeled drug to 5 patients with acute myelocytic leukemia (AML). The levels of unlabeled drug were determined colorimetrically. GZ infected as a tracer dose was rapidly distributed in an apparent volume of 0.61 l/kg, which is somewhat less than that of total body water, and the drug appeared to be eliminated essentially unchanged by glomerular filtration. The mean apparent volume of distribution increased by about 15% during infusion. An increase of 60% was also noted in the half-life (t1/2) values, with a concimitant decrease in the mean value of renal clearance rate by 40%, except in 1 case. The study demonstrates that monitoring levels of guanazole is possible during infusion therapy and indicates that the data could be used to evaluate pharmacokinetic parameters predicting the time-course of such levels in patients.