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The following message was posted to: PharmPK
When comparing steady state (i.e. Day 5, BID PK data) AUCs to an IV single dose, would one use the day 5 AUClast or AUCinfinity. I beleive the Day 5 (steady state) AUClast contains the AUClast-infinity from the previous dose. Therefore the AUClast of the last dose would be compared to AUCinfinity from the single IV dose. Please clarify and/or comment. Thank you
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After multiple dosing, at steady state, AUC (0-inf)single dose = AUC (0-tau) for a drug obeying linear kinetics. Therefore in your example if one was determining absolute oral bioavailability of the drug then one would use the equation:
% oral absolute bioavailability = [AUC (0-tau) after oral dose/AUC (0-inf) after iv dose] x 100. AUC (0-tau) is AUC at steady state during one dose interval. Note that this equation applies to only those drugs that have linear pharmacokinetics..
Hope this helps.
Aziz Karim
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You should compare AUC 0-tau, in your case AUC 0-12 hours, at steady state to AUC 0-infinity after a single dose.
Toufigh
Toufigh Gordi, PhD
President, PK/PD and Clinical Pharmacology Services
Rosa & Co. LLC (www.rosaandco.com)
E-mail: tgordi.aaa.rosaandco.com
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