This is the version of the explanation I wish somebody had given me, written down before I forget what confused me. It is about tirzepatide, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
Steady state is faster than people expect: half-life about five days, so you are at plateau in roughly three to four weeks rather than five. That matters when you are deciding whether a dose step has finished expressing itself.
The condition it depends on
The caveat that the head-to-head used semaglutide 1mg, not 2.4mg. It is still the best direct evidence available, but it is not the comparison most people think they are citing.
The practical version
Practical numbers: half-life about 5 days, steady state 3 to 4 weeks, ladder 2.5 / 5 / 7.5 / 10 / 12.5 / 15mg, and the maintenance doses with published data behind them are 5, 10 and 15mg.
What I am not sure about
The narrow version of the question is how much of the tirzepatide advantage is the GIP component and how much is simply that the dose ladder goes higher in receptor-occupancy terms. I have searched first, so if this is covered somewhere point me at it and I will read it.
— Dr.LeslieOBGYN · corrections welcome and will be edited into this post with credit