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Does extending the interval work as well as reducing the dose?

Asked 18 Sept 2024Modified 19 months agoViewed 52k times
40

My records go back to the first dose with dates, so I can reconstruct the timeline exactly.

These are treated as interchangeable and I do not think they are.

If both are acceptable I would like to know that, so I can stop thinking about it.

Under what conditions does the answer flip?

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DF
askedDr_Colm_Fitzhenry85k24818 Sept 2024
6For what it is worth, my own result was within half a per cent of this. – nkem_obiora 9 months ago
7Any reason this would differ for a longer peptide? – gradient_slope 17 days ago
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3 Answers

Accepted answer first, then by votes
133

Accepted answer

The part that matters: for a compound with a seven-day half-life, dose timing is much less consequential than people expect and dose rate is much more consequential.

Missing a dose by three days on a weekly schedule takes the trough down by less than a factor of 1.35, which is well inside the variation you would see between two on-time weeks. Missing it by five or more days is where the label instructions start to differ between agents, and the reason is how close the next scheduled dose is rather than any mechanistic threshold.

It helps to be literal here: escalating in response to a plateau is a specific and common error of reasoning. A plateau after four to six months is the expected trajectory in every trial in the class — the curve flattens because energy expenditure falls with mass, not because the receptor stopped working. A dose step may still be reasonable; "the loss stopped" is not by itself the reason.

SURMOUNT-1 used a twenty-week escalation of tirzepatide in 2.5 mg increments to maintenance doses of 5, 10 and 15 mg weekly, and reported a clear dose-response across those maintenance levels — which is the closest thing to evidence that the top of the ladder does more than the middle.

The short version: four-week steps because that is steady state, and the ladder is about the side effects, not the result.

edited 5 Oct 2024 by claudia_ferrante — added a caveat about sampling

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answered · acceptedclaudia_ferrante46k3827 Sept 2024
Small correction: the units in the third paragraph should be micrograms, not milligrams. – wren_calloway 4 months ago
2Do you have a reference for the last claim? Not disputing it, just want to read it. – Dr_Wren_Halliday 5 months ago
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38

It helps to be literal here: the titration schedule is a tolerability instrument, not an efficacy one. Nothing in the ladder is there to make the compound work better; every step exists to make the gastrointestinal adverse-event curve survivable.

Holding at a step for longer than four weeks before escalating does appear to reduce cumulative gastrointestinal burden, which is unsurprising given that adverse events cluster in the one to two weeks after each increase. What it does not do is change where you end up, provided you get there.

Stated carefully, the maintenance question turns on what you are maintaining. If the objective is weight maintenance, the withdrawal-extension data suggests that a fraction of the therapeutic dose retains a substantial fraction of the effect. If the objective is the cardiovascular or renal endpoint, the trials that demonstrated those endpoints used the full dose, and extrapolating downward is not supported by anything.

The STEP programme escalated semaglutide over sixteen weeks in four-week steps to 2.4 mg weekly, and the trial-product estimand versus treatment-policy estimand distinction accounts for most of the difference between the figures quoted from those papers.

Escalate on tolerability, hold when it costs you, and do not confuse a flattening curve with a failing drug.

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TH
answeredthreadlock714k263 Jan 2025
-2

More usefully, the steady-state arithmetic is worth doing once, because it explains most of what people find confusing about weekly dosing.

The argument against splitting a weekly dose is arithmetic rather than ideological. Peak-to-trough ratio for a seven-day half-life compound dosed weekly is about two. Split it into twice-weekly and the ratio falls to roughly 1.4. That is a real reduction in fluctuation and a negligible one in absolute terms, and you have doubled the number of stopper piercings and the number of small-volume measurements, each of which carries its own error.

Specifically, where the label ladders differ between agents, the differences track the potency ratio and the tolerability profile rather than anything deeper. It is worth reading the ladders side by side once, because the pattern — small starting dose, four-week steps, a defined maintenance range and a defined maximum — is identical in structure across the class.

The pharmacokinetics of the acylated agonists are well described: absorption from the subcutaneous depot is slow and rate-limiting, the elimination half-life is approximately one week, and steady state is reached in four to five weeks. Every dosing question in this section follows from those three facts.

Write down in advance what would make you hold a step, because deciding that in the middle of a bad week is not when you are at your most analytical.

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DV
answeredDr_Bram_Verhoeven85k2488 Oct 2024
Useful. I have added the accept threshold suggestion to my own notes. – unit_math 8 months ago
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