Four dose steps in, holding each one the full four weeks, and I am trying to work out whether the interval is a pharmacological requirement or a tolerability convention.
The arithmetic in one line: half-life about a week, so steady state at four to five weeks, so a four-week interval is one steady state per step. Two-week intervals mean every step is dosed onto a rising curve.
What I actually want to know is why the interval is four weeks rather than two, and whether a slower ladder gets to the same place.
Tell me what I have not thought of.
This one has a reasonably settled answer, so here it is. Four weeks is the pharmacokinetics, not caution. With a one-week half-life you need four to five half-lives to reach steady state, so at two weeks you are dosing on top of a concentration that has not finished rising. Escalating then stacks exposure and you get the side-effect burden of the higher dose before you have seen the benefit of the current one.
If somebody has the primary source to hand I would rather cite it than paraphrase it.
LabKate said:Four weeks is the pharmacokinetics, not caution.
That is right for the weekly injectables. For the daily agents the interval logic is different and the four-week convention does not transfer.
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Shop Reference StandardsDr.RenalNash said:Four dose steps in, holding each one the full four weeks, and I am trying to work out whether the interval is a pharmacological requirement or a…
Same position here, arrived at the long way round. Holding longer is the underrated move. A step that is uncomfortable at week two is frequently comfortable at week six with no change in dose, because the gastric-emptying component tachyphylaxes while the appetite effect persists. Escalating at week two throws that adaptation away.
From the other side of the consultation, briefly.
Dose escalation anxiety for titration: I was terrified to move from 0.5mg to 1.0mg based on horror stories in this forum. But my actual experience? Slightly more appetite suppression, zero additional side effects.
Remember that the people posting about terrible side effects are a biased sample. Most people titrate up without drama — they just don't post about it because it's uneventful.