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The following message was posted to: PharmPK
Dear all,
To evaluate the stability of a drug in a matrix (for example plasma or
urine), for short and long-term or freeze and thaw stability :
_ Is there any specifications for the age of the matrix ?
_ Does anyone see any alteration of a matrix when it's stored frozen ?
In fact, is there some scientific criteria which tell us to use fresh
matrix for stability studies ?
Clearly,what is the "maximum acceptable age" for a matrix used in
stability
studies ?
Thank you for your help.
A particular thank to Mr Wu for its help.
Regards,
Fabrice Guillet
Bioanalytical Group
Fournier Pharma
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Hi
I think that the matrix properties do alter when frozen. We have
seen differences in protein binding when we use fresh versus frozen
plasma. Hence using fresh matrices (whenever available) is
recommended. From a metabolism point of view, I do not know if
anybody has looked the stability of the esterases in plasma and other
enzymes in other matrices after they have been frozen for a while.
The decrease in activity of the enzyme can result in
misinterpretation of the data.
Deepak Dalvie
Pfizer
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Apart from enzyme activity, pH of the matrix, e.g. plasma, may not
stay the same after freeze and thaw cycle.
Xiaowei
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