On the subject in the title: Semaglutide versus liraglutide head to head: reading STEP 8 carefully Working notes rather than a conclusion.
I would like to disagree carefully with the settled view on semaglutide versus liraglutide, and I would like to be argued out of it if the disagreement is bad.
The disagreement is about one step, not about the conclusion. If the step holds I withdraw it entirely.
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.
Something worth flagging about semaglutide versus liraglutide: the strongest-sounding claims in this thread are the ones with no source attached, which is the usual pattern and not a coincidence.
The opening post describes the usual case. This is about the unusual one.
Cardiovascular data in people without diabetes is the specific contribution of SELECT, and it is worth being precise that the enrolled population had established cardiovascular disease. That is not the same as the general population and the result should not be quoted as though it were.
I checked the source rather than the summary, and they differ.
Building on post #2 rather than restating it.
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 would be glad to be shown a cleaner way of putting this.
Post #4 put the caveat in the right place and I want to underline it.
The oral formulation is a genuinely different pharmaceutical problem from the injectable and shares only the active molecule. Absorption enhancers, fasting requirements and a very different bioavailability mean dose numbers do not translate between the two at all.
A single observation, in a thread that deserves better than single observations.
Offering a way to settle semaglutide versus liraglutide rather than another opinion about it. Two measurements, taken the same way, a fortnight apart. If the difference is within the noise, the question was not answerable at this precision.
On identity confirmation: a mass close to 4113.6 Da on the intact molecule is consistent with semaglutide and is also consistent with several closely related species. Mass narrows the field; it does not close it, and no certificate should be read as though it did.
Marking that as an opinion rather than a finding.
Saving this. It is the version I will quote when the question comes round again.
Answering the question post #7 raises rather than the one it answers.
On the "does it stop working" question: tolerance in the pharmacological sense is not what the withdrawal trials show. What they show is that the effect persists while treatment continues and reverses when it stops, which is a different finding with different implications.
Happy to expand any of that if it is the useful part.
The practical version of semaglutide versus liraglutide is three sentences long. The rigorous version is three pages and reaches the same conclusion with the conditions attached.
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.
Two questions I would want answered before drawing anything from the semaglutide versus liraglutide data above: how were the cases selected, and what happened to the ones that dropped out.
Careful with the language on semaglutide versus liraglutide. "Not detected" and "not present" are different findings and the first is a statement about the method.
Semaglutide's structure is a modified backbone with a C18 diacid attached through a spacer. The acylation is the reason for the long half-life and it is also the reason a plain sequence comparison against native GLP-1 is misleading about how the molecule behaves.
Taking post #15 at face value and following it one step further.
The thing about semaglutide versus liraglutide that took me longest to accept is that a plausible mechanism is not evidence of an effect. It is a reason to look, not a result.
Adding the measurement that post #18 says would settle it.
Solutions of semaglutide can look faintly opalescent without anything being wrong. Visible particulate, fibres or frank cloudiness are a different observation entirely and are worth raising with the supplier rather than reasoning about.
I have seen it go both ways, which is why I hedge.
On the injection-day question: the labelling for licensed semaglutide allows the day to be changed provided at least two days separate the two injections. That interval is not arbitrary — it is what stops two doses stacking inside one absorption window.
Picking up post #20: that is the part I would want checked first.
The opalescent appearance in semaglutide solutions is occasionally noted and the mechanism is unclear. It does not appear to correlate with product failure in practice. Visible particles or frank cloudiness is different and would be reason to contact the supplier.
The strength of my opinion here exceeds the strength of my evidence.
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 number is defensible. The precision I gave it is not.
Discontinuation rates in the trials are worth reading alongside efficacy and almost never are. A large mean effect in a population where a meaningful fraction stopped early is telling you two things, not one.
Nothing above should be read as advice about what anyone else should do.
Helpful, and easy to find again, which is half of what a good reply is.
Picking up post #24: that is the part I would want checked first.
STEP 1 and STEP 4 are two different questions. The first asks what happens when treatment is added; the second asks what happens when it is withdrawn after a run-in. Quoting the first as evidence about maintenance is the commonest misreading of the programme.
That distinction has done more work for me than anything else in this category.
On post #27 — agreed on the reasoning, with one qualification.
The documentation on semaglutide versus liraglutide is better than this thread and I say that as someone who has posted in the thread.
Post #28 is the version of this I will quote in future. One addition.
Research-use-only semaglutide is not a licensed medicine, is not manufactured to pharmaceutical standards, and is not approved for human use. That is a statement about what it is, not a coded opinion about anything.
The step people skip is the one I have spelled out.
My position on semaglutide versus liraglutide is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.