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Dear everybody
I am performing in vitroRBC uptake study of my prodrug A which is
converted to its active metabolite B in vivo. My experimental protocol
goes like this. I spike my drug into preincubated whole blood (for 10
min prior to spiking) to get the desired concentration, say 50 ng/ml.
My stocks are in PBS (so that no hemolysis takes place) and QC of the
spiking solution is checked in advance. I sample whole blood at
different time intervals and also collect plasma from the same time
point. so I have 2 samples per time point, one of whole blood and one
of plasma. When I analysed whole blood at time t=0, the concentration
of A which i got by interpolating from the respective whole blood
calibration curve was 50.2 ng/ml which is expected but at the same time
I also got 10 ng/ml of B at t=0. This happens at other concentration
levels also. How is it possible. There is no flaw as far as spiking and
analysis is concerned.
Thanks in advance
Neeraj
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The following message was posted to: PharmPK
Did you check you concentration of B on your standard curve?
Maybe you have a mixed population of A-B on it (B coming from A
metabolism). This could lead to a decrease of A on your standard curve
and an erroneous determination of A in your experimental sample.
Jose
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The following message was posted to: PharmPK
is this ester hydrolysis of the prodrug?
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The following message was posted to: PharmPK
This may be because that the conversion from A to B also happens inside
the RBC.
There are also some metabolic enzymes inside the RBC. Pls refer to the
reference:
Futile cycling of estrone sulfate and estrone in the recirculating
perfused rat
liver preparation. Tan E, Lu T, Pang KS.J Pharmacol Exp Ther. 2001
Apr;297
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