This is the version of the explanation I wish somebody had given me, written down before I forget what confused me. It is about semaglutide, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
The mechanism that matters here is not stomach emptying, it is central. GLP-1 receptor agonism in the arcuate nucleus stimulates POMC neurons and suppresses AgRP/NPY signalling, which is why the effect is appetite and food salience rather than physical fullness. Delayed gastric emptying largely tachyphylaxes over the first months; the appetite effect does not.
The condition it depends on
That holds for the injectable. The oral formulation has different absorption behaviour and the dose numbers are not interchangeable, which is worth saying out loud because people quote them as if they were.
The practical version
For anyone assembling their own picture: Tmax is one to three days, terminal half-life about 165 to 170 hours, steady state at four to five weeks, and subcutaneous bioavailability near 89%. Those four numbers explain most of the questions people ask about timing.
What I am not sure about
The bit I cannot resolve on my own is whether anyone has held at a sub-maximal dose long term and kept the result, or whether the maintenance data only exists at 2.4mg. Numbers rather than impressions, if you have them.
LondonLisa said:The mechanism that matters here is not stomach emptying, it is central.
Agreed, though "tolerable" needs defining. A dose you tolerate by eating almost nothing is not tolerated, it is being paid for somewhere else — usually in lean mass, sometimes in adherence three months later.
LondonLisa said:The mechanism that matters here is not stomach emptying, it is central.
I will push back on the "any working dose is fine" framing. The maintenance evidence sits overwhelmingly at the top studied dose, and the extension data shows regain tracking dose reduction rather than tracking stopping. Holding low is reasonable; pretending it is evidentially equivalent is not.
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View ResultsTaking the question as asked, rather than the general version of it. Albumin binding above 99% is the whole reason weekly dosing works, and it is also why the trough matters more than the peak. People who dose late are not losing a peak, they are letting the trough fall, and the appetite effect tracks the trough.
RetaRick_CA said:Agreed, though "tolerable" needs defining.
All true, with one condition: that curve is for people who reached the dose on schedule. Anyone who slowed the ladder for tolerability is on a different, flatter curve, and comparing yourself with the published mean will make you feel like a non-responder when you are not.