Circadian rhythm? [Design Issues]

posted by Helmut Homepage – Vienna, Austria, 2024-01-20 13:50 (177 d 15:17 ago) – Posting: # 23834
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Hi NK,

❝ We are planning a steady state bioequivalence study on healthy subject with tid dosing (every 8 hours) on day 1 to day 4. Serial PK blood sample collections are planned on Day 5 after morning dosing(expected to reach steady state concentration on day 5).

❝ Kindly clarify, whether 2nd and 3rd dose on day 5 need to be administered or not? and sampling should be continued for 24 hours?

If you have evidence from peer-reviewed literature that the PK of the drug is not subjected to a circadian rhythm, the profile after the first dose in steady state is sufficient. Otherwise, you have to dose also tid on day 5 and the primary PK metric for the extent of absorption will be AUCss,0–24h. A ‘classical’ example is theophylline.

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