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The following message was posted to: PharmPK
Dear colleagues:
I am dealing with a new formulation of an old drug and
interested to see how the urinary excretion of the two
formulations is comparable. PK studies in patients
receiving the same dose indicate that new formulation
has longer half-life and higher AUC than the old
formulation however this dose not necessarily mean the
% of total dose excreted through the urine is
different. Previous studies with the old formulation
indicate that about 20% (10 to 30%) of the drug is
excreted via the urine in 72 h, which about 50% of it
was parent compound (so about 10% as parent). In
order to determine/compare the urinary excretion of
the new formulation is it ok to use HPLC and do not
use radioisotope? It is more feasible to not to use
radiolabeleld compound (more patient recruitment, not
all the clinical site are capable of handling
radioisotopes, no need to synthesis and characterize
the radiolabeleld compound, ect). The down side of
HPLC is that we would not know exactly what percentage
of the total dose was excreted via the urine. But if
we show that about 10% of the total dose was excreted
as parent compound in the urine can we conclude that
the urinary excretion of the two formulations are
similar? Any comments or insight would be greatly
appreciated.
Rostam
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)