SarahChen_PharmD said:

SURMOUNT-1 landed around 20.9% mean weight loss at 15mg over 72 weeks, against roughly 15% for semaglutide 2.4mg in STEP 1.

Pushing back on SarahChen_PharmD 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.

Dr.ObesityMed said:

The "tirzepatide is simply better" summary irritates me.

Coming at Dr.ObesityMed’s question from a different direction. 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.

Following on from raj_cambridge — and this may be the naive question:

Whether anyone has held 10mg long term rather than climbing, and what happened over the following year?

Reporting back.

Update: the eight-week restart pattern people described is exactly what happened. I nearly abandoned it at week five.