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Dear all,
Just wondering how I can determine the time it'd take for a drug to
reach steady state from a subcutaneous osmotic mini-pump.
I already know the rate of drug delivery, absorption and elimination
rate constants for the drug in question.
Thanks in advance,
Eric Siu
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The following message was posted to: PharmPK
If you know the half time of elimination, first, in a simple model
you steady state could be achieve in 4 to 7 half time of elimination
Thanks
David
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Eric Siu,
The answer to your question can be found in Gibaldi and Perrier
(Pharmacokinetics 2nd Edition, Volume 15). The authors make a clear
mathematical argument for the time to reach steady state.
The conclusion of the exercise states, "For a drug with one-
compartment model characteristics the time required to reach a
particular fraction of steady state is independent of the number of
doses administered and the interval between administrations, but it
is directly proportional to the half-life."
Ultimately:
90% of steady state will be reached in 3.32 half-lives
99% of steady state will be reached in 6.64 half-lives.
Since you have a pump system, you can easily equate your system to a
continuous IV infusion. The concentration-time profile will look
similar to a continuous IV infusion, with concentration starting at
zero and gradually increasing and leveling out until plateau
Thank you
Robert Lepage, M.Sc. CCRP
Pharmacokineticist & Assistant Study Director
Pharma Medica Research Inc.
E-Mail: rlepage.-a-.pharmamedica.com
Phone: (905) 624-9115 x3300
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