Accepted answer
SURMOUNT-1 would have written it into the protocol, and the wording is the part that matters. Escalation protocols in this class generally permit a delay at the current level, sometimes a single step down with a later re-attempt, and count a participant as remaining in the arm throughout. That is analytically important: an intention-to-treat analysis keeps them at their randomised assignment regardless of the dose they were actually taking, so the "top dose" arm contains people who never reached the top dose. Find the protocol amendment history as well as the paper, because tolerability rules are among the things most often revised mid-programme, and dose-escalation decisions are made under supervision — nothing here is medical advice.
The relevant arithmetic is that steady state takes four to five half-lives, so a one-week half-life means a four-week step interval and nothing shorter is informative.
The published tirzepatide schedule steps 2.5, 5, 7.5, 10, 12.5 and 15 mg at four-week intervals, with 2.5 mg as the initiation step rather than a therapeutic one.
Weekly dosing accumulation, 7-day half-life
| Week | Fraction of steady state | Trough as × dose |
|---|
| 1 | 50 % | 0.50 |
| 2 | 75 % | 0.75 |
| 3 | 88 % | 0.88 |
| 4 | 94 % | 0.94 |
| 5 | 97 % | 0.97 |
| 6 | 98 % | 0.98 |
This is why a four-week step interval is approximately, but not exactly, steady state.
Titrating downward is available too. Stepping back and holding is a normal adjustment rather than a failure.
Titration schedules in the licensed products were designed specifically to manage gastrointestinal tolerability, and that intent is stated in the clinical development literature.
Faster titration does not reach the destination sooner in any way that matters; it reaches the symptoms sooner.
Slower costs time and nothing else. The ceiling is the same.
4Two of us compared schedules and the difference was entirely in patience. – amara_nwachukwu 8 months ago 5Does the same interval logic apply to the daily agents, or is it shorter? – Dr_Ilse_Vandenberg 10 months ago add a comment