Pharmacokinetic study of fludarabine phosphate (NSC 312887)

Characterization of the pharmacokinetics of 2-FLAA has been completed in seven patients receiving 18 or 25 mg/m2 daily X 5 of 2-FLAMP over 30 min. Assuming 2-FLAMP was instantaneously converted to 2-FLAA, the plasma levels of 2-FLAA declined in a biexponential fashion. Computer fitting of the plasma concentration-time curves yielded an average distribution half-life (t1/2 alpha) of 0.60 h and a terminal half-life (t1/2 beta) of 9.3 h. The estimated plasma clearance was 9.07 +/- 3.77 l/h per m2 and the steady state volume of distribution, 96.2 +/- 26.0 l/m2. There was a significant inverse correlation between the area under the curve (AUC) and absolute granulocyte count (r = -0.94, P less than 0.02). A relationship between creatinine clearance and total body clearance was noted, but was not statistically significant (r = 0.828; P less than 0.1). Approximately 24% +/- 3% of 2-FLAA was excreted renally over the 5-day course of drug administration.