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The following message was posted to: PharmPK
I would like to know some opinions about the use of Internal standard
for
bioanalytical studies in regulatory preclinical (toxicokinetics) and
clinical studies, with LC-MS methods. As you know the internal standard
could be stable isotope (H-2 or C-13) of the
compound of interest) or a similar compound.
The FDA or EMEA have some regulations or preferences about these
options? What is the best option?
Is possible to validate methods in preclinical with the second
option
(similar compound) and after using the label compound (H-2 or
C-13)in
clinical studies?
thanks
Benjamin Santos Ph.D.
Pharmacokinetics and Metabolism Dept.
R&D Center, Ferrer Internacional S.A.
Juan de Sada 32, 08028 Barcelona, Spain
Tel. +34 93 509 32 30, Fax +34 93 411 27 64
E-mail bsantos-research.-a-.ferrergrupo.com
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The following message was posted to: PharmPK
As long as you validate the method according to the FDA guidelines for
bioanalytical methods, you could use a similar compound (structural
analog) instead of an isotopic analog as an internal standard.
Isotopic analog internal standards need to be well resolved in mass from
the analyte.
My experience is that for LCMS assays, isotopic analogs generally give
more consistent and reproducible results than structural analogs, though
there are assays with structural analogs that wok just fine for specific
analytes.
Tom
Thomas L. Tarnowski, Ph. D.
Project Team Leader
Group Leader /Dept. Head, Drug Metabolism and Pharmacokinetics
Roche Palo Alto
3431 Hillview Avenue, Palo Alto, CA 94304
* Phone: (650) 852-3182
* FAX: (650) 855-6428
* email tom.tarnowski.-at-.roche.com
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)