Coming back to: Semaglutide half-life: where the 165 to 184 hour figure comes from posts 91–120

Building on post #104 rather than restating it.

I think the Semaglutide half-life question is answerable and has not been answered, which is a more optimistic position than most of this thread.

The C-cell question: semaglutide triggered medullary thyroid carcinoma in rodent toxicology studies. A signal in rodents does not automatically appear in humans, but it is the reason the compound is contraindicated in people with personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2.

Worth checking against a second source before it gets quoted onward.

Where the Semaglutide half-life reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.

A note on scope: what I am saying about Semaglutide half-life applies to the case in the first post and I would not extend it further without checking.

Semaglutide versus liraglutide in STEP 8: semaglutide produced greater weight reduction and the discontinuation rates differed. But the trial was open-label for the dosing schedule, which admits expectation effects. Weekly versus daily itself is part of the comparison, not a confounding variable to be removed.

The variance between people here is larger than the effect being discussed.

Understood, and I withdraw the assumption I opened with.

The mass figure differs between sources because of how the different entities report it. The monoisotopic mass of the bare peptide is one number; the mass including the acylation is another. Different sources emphasise different details.

On balance I think that is right, and I would not bet much on it.

Semaglutide half-life: I would want to see the raw numbers rather than the summary before agreeing. Summaries lose exactly the information that would settle this.

The 165 to 184 hour range: that is roughly 7 to 7.6 days, which is why the weekly schedule works. Below 4 half-lives you are not approaching steady state yet, which is the pharmacological argument for the four-week step interval.

Adding the measurement that post #113 says would settle it.

Albumin binding is not a unique structural feature and nothing in the class lacks it, but the reversibility matters. Semaglutide binds albumin covalently through a fatty side chain, which creates a very long half-life at the cost of sequestering the free form. That is a trade-off and it is the trade-off that allows weekly dosing.

A weak preference rather than a position.

Small correction to my own earlier position on Semaglutide half-life. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.

Appreciated. The plain phrasing does more work here than a longer post would.

On alcohol: the labelling does not contraindicate it, but it raises gastric irritation risk and semaglutide already does that. There is no published interaction study and the conservative position is to limit it if you are titrating or if gastrointestinal symptoms are troublesome.

Nobody has said the unglamorous part of Semaglutide half-life yet, so: most of the variation is explained by things that are boring to write about and easy to check.

Taking post #118 at face value and following it one step further.

Injection site does not appear to matter much for semaglutide exposure. The published comparisons of abdomen, thigh and upper arm found differences small enough to be clinically unimportant, which is not true of every injectable.

I am aware this is the third time this month I have made this point.