Collecting this in one place because it comes up every few weeks and the answer is always assembled from scratch. It is about semaglutide, and it is deliberately narrow — everything I am not confident about is marked as such.
The dose-response is real but shallow at the top. Across STEP 1 and STEP 4 the gap between 1.7mg and 2.4mg is a couple of percentage points of body weight on average, and the average is carrying a wide spread — plenty of people at 1.7mg sit above the 2.4mg mean. If a dose is working and tolerable, "working" is the relevant variable, not "maximal".
"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.
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 trying to establish is how much of the between-person variation is pharmacokinetic and how much is just adherence measured badly. Tell me what I have not thought of.
jason_sac26 said:The dose-response is real but shallow at the top.
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.
jason_sac26 said:The dose-response is real but shallow at the top.
This is where I part company with the consensus forming above. The trial means are being read too generously in this thread. STEP populations were selected, supported, and titrated by protocol, and the real-world curves are consistently a few points worse. That difference is not noise, it is what happens when you remove the study infrastructure.
Ask again with the specifics and you will get a better answer than this one.
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Browse GL BiochemThis one has a reasonably settled answer, so here it is. Steady state is the thing most people miss. The terminal half-life is about a week, so every dose step takes four to five weeks to fully express itself. Judging a step at day ten is judging the ascent, not the plateau, and it is the single commonest reason people escalate before they needed to.
CarlaRPh_TPA said:All true, with one condition: that curve is for people who reached the dose on schedule.
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.