Sensitive and rapid quantification of busulfan in small plasma volumes by liquid chromatography-electrospray mass spectrometry.
BACKGROUND
High-dose busulfan is widely used in conditioning regimens before hematopoietic stem cell transplantation in both adults and children. Large interindividual variability in pharmacokinetics after oral administration has been reported; therefore, therapeutic drug monitoring of busulfan may decrease the incidence of drug-related toxicity (for example, hepatic venoocclusive disease) and may also improve therapeutic efficacy.


METHODS
Busulfan concentrations were quantified using 200 microL of plasma and liquid-liquid extraction with diethyl ether after the addition of [2H8]busulfan as the internal standard. Separation and detection of busulfan and [2H8]busulfan were achieved with a LUNA C8 column (5 microm; 150 x 2 mm i.d.) at 30 degrees C, a HP 1100 liquid chromatography system, and a HP 1100 single-quadrupole mass spectrometer. Busulfan and [2H8]busulfan were detected as ammonium adducts in selected-ion monitoring mode at m/z 264.2 and 272.2, respectively.


RESULTS
The calibration curve was linear at 5-2000 microg/L busulfan. Intra- and interassay imprecision (CV) and bias were both <11%. The limits of detection and quantification were 2 and 5 microg/L, respectively. Extraction recovery of busulfan was >87%. Analysis of pharmacokinetics in four patients receiving high-dose busulfan indicated that minimum busulfan concentrations before the next dose were 405-603 microg/L, with no interference observed.


CONCLUSIONS
The new rapid and sensitive liquid chromatographic-mass spectrometric assay is an appropriate method for quantification of busulfan in human plasma, making therapeutic drug monitoring of busulfan faster and easier in clinical practice.
Mürdter
T E
TE
Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112, D-70376 Stuttgart, Germany. thomas.muedter@ikp-stuttgart.de
Coller
J
J
Claviez
A
A
Schönberger
F
F
Hofmann
U
U
Dreger
P
P
Schwab
M
M
D000293:Adolescent; D000328:Adult; D018906:Antineoplastic Agents, Alkylating / Q000097:blood*; D002066:Busulfan / Q000097:blood*; D002853:Chromatography, Liquid; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization
D018906:Antineoplastic Agents, Alkylating; D002066:Busulfan