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Compounds · Semaglutide

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

I
IHollingworthTL2Member18 May 2025#1

Semaglutide half-life: where the 165 to 184 hour figure comes from Writing it up because I had to work it out twice and would rather nobody else did.

I have seen SUSTAIN 6 (N Engl J Med, 2016) cited in support of a claim I do not think it supports, twice this month, so I would like to work through what it actually shows.

My reading is that the trial is sound for its own question and is being stretched to answer a different one. I might be wrong about that, which is why this is a topic rather than a correction.

What I would like from this discussion: someone who disagrees with me to say why, with the section of the paper they are relying on.

39 likes 14mo
CN
cannula_notesTL2Member20 May 2025#2

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.

9 likes 14mo
TL
t.lindqvistTL2 Moderator21 May 2025#3

I read the opening post twice before replying, because I had assumed the opposite.

Gastric emptying delay is the mechanism behind most of the gastrointestinal side effects. Slowing the stomach empties it feeds less food into the intestines at a time, which is part of the satiety mechanism but is also why nausea is dose-dependent and titration-dependent.

0 likes 14mo
M
MSaarinenTL3Regular23 May 2025#4

This follows post #3 rather than contradicting it.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

0 likes 14mo
SO
sa.okonkwoTL2 Moderator24 May 2025#5
MSaarinen, post #4: This follows post #3 rather than contradicting it. For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use. Go to post

On the opening post — agreed on the reasoning, with one qualification.

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.

15 likes in reply to #4 14mo
JD
j.delacroixTL3Regular25 May 2025#6

Approved indications differ by jurisdiction and change. As of mid-2026 the weight-management indication is approved in many European jurisdictions but not all, and access is still narrower in others. For your own region, check the regulatory website rather than a forum summary.

5 likes 14mo
MM
m.malinowskiTL2 Moderator26 May 2025#7

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

0 likes 14mo
AW
a.westergaardTL3Regular27 May 2025#8

Picking up post #5: that is the part I would want checked first.

Is there a ceiling dose beyond which the effect plateaus? The trials did not study that because they stopped at 2.4 mg. Some people report trying higher doses, but trial data is absent and off-label dosing enters territory this site does not advise on.

30 likes 14mo
AA
a.almeidaTL2 Moderator28 May 2025#9

Worth separating two things that post #5 runs together.

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.

0 likes 14mo
PS
p.silvaTL2 Moderator29 May 2025#10
j.delacroix, post #6: Approved indications differ by jurisdiction and change. As of mid-2026 the weight-management indication is approved in many European jurisdictions but not all, and access is still narrower in others. For your own region, check the regulatory website rather than a forum summary. Go to post

post #9 is right about the mechanism and I think understates the practical bit.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.

20 likes in reply to #6 14mo
GD
g.danquahTL2 Moderator30 May 2025#11

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.

32 likes 14mo
B
BuchholzTL2Member31 May 2025#12

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

0 likes 14mo
EK
ew.kuuselaTL2 Moderator1 Jun 2025#13
j.delacroix, post #6: Approved indications differ by jurisdiction and change. As of mid-2026 the weight-management indication is approved in many European jurisdictions but not all, and access is still narrower in others. For your own region, check the regulatory website rather than a forum summary. Go to post

Picking up post #10: that is the part I would want checked first.

The SELECT trial changed the positioning because it was the first cardiovascular outcome trial in people without diabetes. That decoupled the cardiovascular argument from glycaemic control, which is why it mattered beyond its own numbers.

6 likes in reply to #6 14mo
TW
t.waldenstrmTL2Member2 Jun 2025 · edited#14
p.silva, post #10: post #9 is right about the mechanism and I think understates the practical bit. Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up. Go to post

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.

16 likes in reply to #10 14mo
SR
s.radichTL2 Moderator3 Jun 2025#15

The STEP programme populations were selected: enrollment criteria required baseline body mass index over 30, no recent blood pressure crisis, no recent retinopathy, no renal disease at the time. Applying results from that population to someone well outside it is an extrapolation and should be called one.

24 likes 14mo
KB
k.bettencourtTL2Member4 Jun 2025#16

Worth separating two things that post #12 runs together.

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.

0 likes 14mo
JS
j.solbergTL2 Moderator5 Jun 2025#17

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.

3 likes 14mo
L
LundqvistTL2Member6 Jun 2025#18
s.radich, post #15: The STEP programme populations were selected: enrollment criteria required baseline body mass index over 30, no recent blood pressure crisis, no recent retinopathy, no renal disease at the time. Applying results from that population to someone well outside it is an extrapolation and should be called one. Go to post

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.

11 likes in reply to #15 14mo
FL
f.laurentTL2 Moderator7 Jun 2025#19

post #18 answers the question as asked. The question underneath it is different.

The STEP programme populations were selected: enrollment criteria required baseline body mass index over 30, no recent blood pressure crisis, no recent retinopathy, no renal disease at the time. Applying results from that population to someone well outside it is an extrapolation and should be called one.

0 likes 14mo
SE
septum_entryTL2Member8 Jun 2025#20
p.silva, post #10: post #9 is right about the mechanism and I think understates the practical bit. Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up. Go to post

Gastric emptying delay is the mechanism behind most of the gastrointestinal side effects. Slowing the stomach empties it feeds less food into the intestines at a time, which is part of the satiety mechanism but is also why nausea is dose-dependent and titration-dependent.

3 likes in reply to #10 14mo
JF
j.falkTL2 Moderator9 Jun 2025#21

Worth separating two things that post #17 runs together.

The SELECT trial changed the positioning because it was the first cardiovascular outcome trial in people without diabetes. That decoupled the cardiovascular argument from glycaemic control, which is why it mattered beyond its own numbers.

0 likes 14mo
YM
y.mensahTL3Wiki editor10 Jun 2025#22

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.

23 likes 14mo
IW
i.wojcikTL2 Moderator10 Jun 2025#23
m.malinowski, post #7: Two things before anyone answers the substance. First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound. Go to post

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.

10 likes in reply to #7 14mo
BJ
b.jankowiakTL3Regular11 Jun 2025#24

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.

3 likes 14mo
BW
b.wikstromTL2 Moderator12 Jun 2025#25

On post #21 — agreed on the reasoning, with one qualification.

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.

32 likes 14mo
BE
bench_entryTL3Regular13 Jun 2025#26

post #25 answers the question as asked. The question underneath it is different.

Is there a ceiling dose beyond which the effect plateaus? The trials did not study that because they stopped at 2.4 mg. Some people report trying higher doses, but trial data is absent and off-label dosing enters territory this site does not advise on.

16 likes 13mo
FL
f.lindholmTL2 Moderator14 Jun 2025#27
j.delacroix, post #6: Approved indications differ by jurisdiction and change. As of mid-2026 the weight-management indication is approved in many European jurisdictions but not all, and access is still narrower in others. For your own region, check the regulatory website rather than a forum summary. Go to post

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.

6 likes in reply to #6 13mo
BS
buffer_sheetTL3Regular15 Jun 2025#28

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

1 like 13mo
RF
ro.friskTL2 Moderator15 Jun 2025#29

Approved indications differ by jurisdiction and change. As of mid-2026 the weight-management indication is approved in many European jurisdictions but not all, and access is still narrower in others. For your own region, check the regulatory website rather than a forum summary.

24 likes 13mo
DS
dr_seongTL3Physician16 Jun 2025#30
b.wikstrom, post #25: On post #21 — agreed on the reasoning, with one qualification. 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. Go to post

post #29 is right about the mechanism and I think understates the practical bit.

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.

11 likes in reply to #25 13mo