A limited sampling schedule to estimate individual pharmacokinetic parameters of fludarabine in hematopoietic cell transplant patients.
OBJECTIVE
Fludarabine monophosphate (fludarabine) is frequently administered to patients receiving a reduced-intensity conditioning regimen for allogeneic hematopoietic cell transplant (HCT) in an ambulatory care setting. These patients experience significant interpatient variability in clinical outcomes, potentially due to pharmacokinetic variability in 2-fluoroadenine (F-ara-A) plasma concentrations. To test such hypotheses, patient compliance with the blood sampling should be optimized by the development of a minimally intrusive limited sampling schedule (LSS) to characterize F-ara-A pharmacokinetics. To this end, we sought to create the first F-ara-A population pharmacokinetic model and subsequently a LSS.


METHODS
A retrospective evaluation of F-ara-A pharmacokinetics was conducted after one or more doses of daily i.v. fludarabine in 42 adult HCT recipients. NONMEM software was used to estimate the population pharmacokinetic parameters and compute the area under the concentration-time curve.


RESULTS
A two-compartment model best fits the data. A LSS was constructed using a simulation approach, seeking to minimize the scaled mean squared error for the area under the concentration-time curve for each simulated individual. The LSS times chosen were 0.583, 1.5, 6.5, and 24 hours after the start of the 30-minute fludarabine infusion.


CONCLUSIONS
The pharmacokinetics of F-ara-A in an individual HCT patient can be accurately estimated by obtaining four blood samples (using the LSS) and maximum a posteriori Bayesian estimation.


CONCLUSIONS
These are essential tools for prospective pharmacodynamic studies seeking to determine if clinical outcomes are related to F-ara-A pharmacokinetics in patients receiving i.v. fludarabine in the ambulatory clinic.
Salinger
David H
DH
Department of Bioengineering, University of Washington, Seattle, Washington 98195-7630, USA.
Blough
David K
DK
Vicini
Paolo
P
Anasetti
Claudio
C
O'Donnell
Paul V
PV
Sandmaier
Brenda M
BM
McCune
Jeannine S
JS
D000293:Adolescent; D000328:Adult; D000368:Aged; D001800:Blood Specimen Collection / Q000379:methods*; D002648:Child; D005260:Female; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D012189:Retrospective Studies; D013997:Time Factors; D019172:Transplantation Conditioning / Q000379:methods; D001084:Vidarabine Phosphate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D055815:Young Adult
D007166:Immunosuppressive Agents; D001084:Vidarabine Phosphate; C042382:fludarabine phosphate