Does splitting a 12 mg weekly dose of orforglipron across two administrations change anything?

Details up front: 12 mg · orforglipron.

I suspect the usual explanation for this is wrong, or at least incomplete.

I am aware this may have a boring answer. I would still like the boring answer stated clearly.

Can someone derive this rather than assert it?

Two administrations of 6 mg instead of one of 12 mg — the same 12 mg a week either way. Total weekly exposure is unchanged; what changes is the peak-to-trough ratio, and for an agent with a half-life measured in days the trough barely moves because the dosing interval is already short relative to it. The arithmetic is the easy part: 12 ÷ 2 = 6. Whether it is worth doing is a pharmacokinetic question, and nothing here is medical advice.

The honest answer is that reported tolerability benefits are real to the people reporting them and are not well explained by the exposure profile.

For a drug with elimination half-life t½ dosed at interval τ, the peak-to-trough ratio at steady state is 2^(τ/t½). With a one-week half-life dosed weekly, τ/t½ = 1, so the ratio is 2 — a factor of two between peak and trough, which is already flat by pharmacological standards.

Stated carefully, accumulation to steady state takes four to five half-lives regardless of how the dose is divided. Splitting does not shorten it and does not change the average exposure.

The caveat is that no split schedule has been evaluated in a trial, so the whole discussion is inference plus report.

If you cannot read half the dose accurately, you cannot split it accurately.