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Dear all,
I recently face one question on the Tmax variation in clinical PK. The detail is as immediate
release tablet, 8 HVs, the Tmax from 1.5 hrs to 5 hrs. It's a normal range, or abnormal? Any
reasons, difference from test subjects or formulation?
Thanks a lot!
Fred
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Dear Fred,
How flat is the CP-time curve? How sparse are the sampling times? If the
curve is relatively flat, then the time of maximum concentration will vary
more than if it is very sharp.
By the way, when is the highest observed concentration equal to Cmax?
NEVER! (For all practical purposes)
Why? Because we can¹t sample at exactly Tmax - we have no idea when it
will occur! So the odds of taking a sample exactly at Tmax are vanishingly
small. We may be very close, or we may be very far away. The Tmax and Cmax
predicted by a good model will be far better estimates than the highest
observed concentration (unless you are VERY lucky, but you won¹t know that
until you build a good model and compare).
So Tmax is never the time that the highest observation was made (it might
be close, or it might not).
Best regards,
Walt
Walt Woltosz
Chairman and CEO
Simulations Plus, Inc. (NASDAQ: SLP)
42505 10th Street West
Lancaster, CA 93534
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