Dear Group,Back to the Top
Invariably many of the us in pharmacokinetics need to
address the methods that have been employed to determine the unbound
NCE'S concentrations in plasma viz., Ultrafiltration and Equilibrium
dialysis followed by HPLC assays,where non-specific binding onto the
membrane and leakage of bound drug through the membrane are the major
limitaion factors. These problems become serious especially when you
deal with highly protein bound NCE's.
Protein binding manifests to be the major factor in
determining several PK parameters and interspecies scaling as well
(Bcoz of differences in amino acid sequence in different animal
species, seum albumin of different animal species may exhibit different
binding ability).
Insight into the literature reveals that High performance
frontal analysis (HPFA) effectively answers the problems coupled with
conventional methods.Simple HPLC system can be readily incorporated
with HPFA column such as develosil 100 diol 5 and extraction column
such as Wakosil 5C4 with simple phosphate buffer at physiological pH so
as to maintain the equilibrium, enables you to inject plasma samples
directly onto the column.HPFA allows you to estimate both free drug vis
a vis total drug concentration in a single run. By coupling it into
chiral column you can also estimate protein binding of individual
enantiomers with high accuracy.
Unbound Troglitazone ( Bound 99.89%) was determined with good
reproducibility by using a simple UV DETECTION .at. 280NM (A. Shibukawa,
T. Sawada, C. Nakao, T. Izumi and T. Nakagawa, J. Chromatogr. A, 697
(1995) 337).
Looking into the merits one can enjoy with HPFA, I request
anyone from PharmPk group who already translated HPFA into practice to
recommend and suggest the use of it in a routine analysis and pros and
cons as well. Also I welcome the suggestions onany alternative, simple
and robust method meant for protein binding analysis in use with
accuracy and reproducibility. Thanks in advance
With Regards,
S Syed Mustafa,
Research Associate,
Drug Metabolism & Pharmacokinetics,
Dr Reddy's Research foundation,
Bollaram Road, Miyapur,
Hyderabad-500049 INDIA
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)