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The following message was posted to: PharmPK
Hello,
I would like to determine blood to plasma ratio for my drug which is
not radiolabelled. Most of the published methods include the use of
labelled drugs. If someone has any information in the respect, kindly
let me know.
Thanks
Avantika Barve
Rutgers University
Piscataway, NJ
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The following message was posted to: PharmPK
Avantika,
While the use of radiolabelled compound makes blood-to-plasma ratio
assessment relatively easy, it may not always be the accurate means of
estimation especially when the compound in question is unstable.
So, use of cold compound is after all not a bad idea provided you have
an analytical method that is both selective and sensitive enough to
serve your purpose. Spike an aliquot of the drug solution (say 10 uL) at
a concentration of your interest into an aliquot (say 1 mL each) of
whole blood and plasma (control), let it equilibrate for whatever time
you deem appropriate and take an aliquot of plasma (say 50/100 uL, in
case of whole blood - spin enough blood to obtain required plasma
volume) and measure the drug concentration. The blood-to-plasma ratio
will be the ratio of drug in plasma (control) to the concentration of
drug in plasma fraction (obtained from whole blood). A ratio of 1
indicates equal distribution of drug between plasma and RBCs while a
ratio greater than 1 indicates preferential partitioning into RBCs and
ratio lower than 1 indicates affinity to plasma proteins.
Cheers,
Kasiram.
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The following message was posted to: PharmPK
Dear Avantika,
You may refer to the following review article for detailed description.
Peter H. Hinderling. Red Blood Cells: A Neglected Compartment in
Pharmacokinetics and Pharmacodynamics. Pharmacological Reviews. Vol
(49), No 3, 1997 (279-295).
The following research article gives an overview of procedure.
Nitin Mehrotra, Jawahar Lal, Sunil Kumar Puri, Kunnath P. Madhusudanan,
Ram Chandra Gupta. In Vitro and In Vivo pharmacokinetic studies of
bulaquine (analogue of primaquine), a novel antirelapse antimalarial, in
rat, rabbit and monkey - highlighting species similarities and
differences. Biopharmaceutics & Drug Disposition. Vol 28, Issue 5, 2007
(209-227).
Hope this helps
Regards
Sivacharan Kollipara
Research Associate
Metabolism & Pharmacokinetics
Ranbaxy Laboratories Ltd
India
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If you have a specific blood and plasma assay (ie lc/ms), then can
determine B/P ratios for parent and metabolites. Stanley Cotler
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