DataDave said: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.
Pushing back on DataDave here. The "tirzepatide is simply better" summary irritates me. It is better on mean weight loss, and the cardiovascular outcome evidence is far thinner than semaglutide's. If the reason for treating is cardiovascular risk rather than weight, the evidence base points the other way.
The figures, for anyone assembling their own picture. Numbers worth memorising for this class: Tmax one to three days for the weekly peptides, terminal half-life about a week for semaglutide and about five days for tirzepatide, steady state at four to five half-lives, subcutaneous bioavailability high enough that site choice is irrelevant.
I would rather be corrected than agreed with, if it comes to it.
PharmD_Rodriguez said:The "tirzepatide is simply better" summary irritates me.
Adding the part of the answer the thread has not reached. The pharmacokinetics explain nearly every practical question asked here. Albumin binding above 99% slows clearance enough to make weekly dosing possible; a terminal half-life near a week means four to five weeks to steady state and therefore a four-week titration interval; subcutaneous bioavailability around 89% means injection site barely matters. Those three facts answer most timing questions before they are asked.
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View ResultsOne thing that is still open after traveltech_sara’s answer:
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?
OP back with an update, since a thread like this is useless without one.
Update: the eight-week restart pattern people described is exactly what happened. I nearly abandoned it at week five.