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Sensitive and specific chromatographic methods for the pharmacokinetic evaluation of carboplatin in young patients Burns, Robbin Bruce
Abstract
Carboplatin, c/s-diamminedichloro-1,1-cyciobutanedicarboxylatoplatinum II, is a second generation platinum antineoplastic agent that cross-links DNA. Dosing of carboplatin in adults is frequently based on formulas that relate renal elimination to AUC. Pharmacokinetic studies evaluating these dosing schemes are complicated by the assay methods utilized. In particular, substitution of platinum for carboplatin measurements in pharmacokinetic studies has occurred due to the poor sensitivity of existing HPLC assays for the parent drug. The objectives of this study were (1) to develop and validate a sensitive and specific HPLC assay method for determination of carboplatin in plasma ultrafiltrate, and (2) to compare carboplatin AUC estimates determined using free (non protein-bound) carboplatin versus estimates using free platinum. Assay methods for quantitation of carboplatin were developed utilizing HPLC with direct UV detection and with UV detection following post-column (PC) derivatization. Both methods yielded quantitation limits that were approximately 10-fold more sensitive than previous HPLC-UV methods. For the HPLC-PC method, sodium bisulfite was used to derivatize carboplatin to products possessing enhanced UV absorbance at 290 nm. The greater selectivity of this analytical wavelength removed the need for sample extraction, resulting in a simpler and more rapid assay procedure. MethCBDCA (bis(methylamine)cyclobutanedicarboxylatoplatinum II) and MethMal (bis(methylamine)malonatoplatinum II) were synthesized as internal standards for the HPLC-UV and HPLC-PC methods, respectively, the chemical structures being confirmed by HPLC-MS under positive electrospray ionization conditions. Both HPLC-UV and HPLC-PC methods were validated for carboplatin concentrations from 0.05 to 40 |ag/mL. Validated assay parameters included limits of detection and quantitation, specificity, precision, accuracy, linearity, and ruggedness. Recovery and stability were examined using the HPLC-UV method only. Assay variability was much higher for the HPLC-PC method due to time-dependent changes in signal response caused by the degradation of the post-column reagent, sodium bisulfite. The more precise HPLC-UV method was used in the pharmacokinetic study. The pharmacokinetic behaviour of carboplatin during eight cycles of chemotherapy in two young patients was investigated. Carboplatin concentrations in plasma ultrafiltrate were determined by the HPLC-UV method, while plasma ultrafiltrate platinum concentrations were determined by atomic absorbance. Based on visual examination of the concentration-time profiles, free carboplatin and free platinum elimination were clearly different. To better characterize the magnitude of the differences, AUC estimates derived from free platinum data were compared to those derived from free carboplatin data. The free platinum AUC estimates were as much as two-fold greater than their free carboplatin counterparts. However, the observed differences were much smaller in one patient than in the other. Further study is needed to more accurately characterize the extent of these differences across a larger patient population. Currently, we recommend that HPLC and AA assay methods not be used interchangeably for determination of carboplatin pharmacokinetic parameters.
Item Metadata
Title |
Sensitive and specific chromatographic methods for the pharmacokinetic evaluation of carboplatin in young patients
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2000
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Description |
Carboplatin, c/s-diamminedichloro-1,1-cyciobutanedicarboxylatoplatinum II, is a
second generation platinum antineoplastic agent that cross-links DNA. Dosing of
carboplatin in adults is frequently based on formulas that relate renal elimination to
AUC. Pharmacokinetic studies evaluating these dosing schemes are complicated by
the assay methods utilized. In particular, substitution of platinum for carboplatin
measurements in pharmacokinetic studies has occurred due to the poor sensitivity of
existing HPLC assays for the parent drug. The objectives of this study were (1) to
develop and validate a sensitive and specific HPLC assay method for determination of
carboplatin in plasma ultrafiltrate, and (2) to compare carboplatin AUC estimates
determined using free (non protein-bound) carboplatin versus estimates using free
platinum.
Assay methods for quantitation of carboplatin were developed utilizing HPLC with
direct UV detection and with UV detection following post-column (PC) derivatization.
Both methods yielded quantitation limits that were approximately 10-fold more sensitive
than previous HPLC-UV methods. For the HPLC-PC method, sodium bisulfite was
used to derivatize carboplatin to products possessing enhanced UV absorbance at 290
nm. The greater selectivity of this analytical wavelength removed the need for sample
extraction, resulting in a simpler and more rapid assay procedure.
MethCBDCA (bis(methylamine)cyclobutanedicarboxylatoplatinum II) and
MethMal (bis(methylamine)malonatoplatinum II) were synthesized as internal standards
for the HPLC-UV and HPLC-PC methods, respectively, the chemical structures being
confirmed by HPLC-MS under positive electrospray ionization conditions. Both HPLC-UV
and HPLC-PC methods were validated for carboplatin concentrations from 0.05 to
40 |ag/mL. Validated assay parameters included limits of detection and quantitation,
specificity, precision, accuracy, linearity, and ruggedness. Recovery and stability were
examined using the HPLC-UV method only. Assay variability was much higher for the
HPLC-PC method due to time-dependent changes in signal response caused by the
degradation of the post-column reagent, sodium bisulfite. The more precise HPLC-UV
method was used in the pharmacokinetic study.
The pharmacokinetic behaviour of carboplatin during eight cycles of
chemotherapy in two young patients was investigated. Carboplatin concentrations in
plasma ultrafiltrate were determined by the HPLC-UV method, while plasma ultrafiltrate
platinum concentrations were determined by atomic absorbance. Based on visual
examination of the concentration-time profiles, free carboplatin and free platinum
elimination were clearly different. To better characterize the magnitude of the
differences, AUC estimates derived from free platinum data were compared to those
derived from free carboplatin data. The free platinum AUC estimates were as much as
two-fold greater than their free carboplatin counterparts. However, the observed
differences were much smaller in one patient than in the other. Further study is needed
to more accurately characterize the extent of these differences across a larger patient
population. Currently, we recommend that HPLC and AA assay methods not be used
interchangeably for determination of carboplatin pharmacokinetic parameters.
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Extent |
8603831 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0089694
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2000-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.