Bioequivalence and Bioavailability Forum

Dear Helmut!

❝ ❝ This is my 1st post here and excited to learn/share science.

❝ Welcome to the club.

Thank you very much for your kind welcome.

❝ Do you know more about the drug than its t_max? Further, t_max = 8.4 h is not set in stone. Profiles of SR formulations are sometimes pretty flat. C_max is a composite PK metric (depends not only on \(\small{k_\text{a}}\) but also on \(\small{k_\text{e}}\) and \(\small{f}\)) and therefore, a poor predictor of \(\small{k_\text{a}}\). Since \(\small{k_\text{a}}\) varies between subjects, I would add more sampling time points around the anticipated t_max.

About the Drug - Since the study is a simulation-based experiment, I developed a hypothetical drug which is expected to have more colonic absorption to support my theoretical objective.

I have pasted the Log-Conc profile of the drug for your reference below.

I totally agree with you point regarding Cmax. But also I want to be realistic in PK sampling time points to clinical setting. I mean, no over-sampling. therefore, according to US FDA guidance "Bio­equivalence Studies With Pharmacokinetic End­points for Drugs Submitted Under an ANDA Guidance for Industry, 2021", I can go upto 18 time points.

In my case, I do not see flip-flop kinetics, therefore I will assume the Tmax = 8.4 h as reliable parameter and add further more (3-5) time points.

I also would like to know, what are the criteria to choose the PK sampling time points as best as possible to capture the PK estimates well? (All I know to describe the ADE phase and at least three or more terminal elimination half-lives of the drug).

Kindly correct me if I am wrong in my assumptions.

Thanks a lot and open for comments!

Best Regards,
Titus