Accepted answer
36 mg a week is 5.143 mg a day averaged out and 1872 mg over a year — but "defensible" is not a property of the number, it is a property of where the number came from. A maintenance dose is defensible when a trial randomised people to it and reported what happened, and indefensible when it was arrived at by interpolation between two doses that were studied. So the question to ask of 36 mg is which arm it corresponds to: if a programme ran 36 mg as a maintenance level, there is an efficacy figure, a tolerability figure and a discontinuation rate attached to it. If it sits between two studied levels, everything said about it is extrapolation, and the burden of that is on whoever proposed it. The other half of the arithmetic is supply: at 36 mg a week a 10 mg vial is 0.28 weeks and you will need about 188 of them a year, which is worth knowing before the dose is settled rather than after. Maintenance doses are set by a prescriber against an individual; nothing here is medical advice.
The relevant observation is that maintenance frequently requires less exposure than the loss phase did, and the trials suggest it rather than establish it.
A downward search proceeds one step at a time with at least eight weeks at each level, because a weekly agent takes four to five weeks to reach the new steady state and then needs time for the trend to be readable.
Weekly dosing accumulation, 7-day half-life
| Week | Fraction of steady state | Trough as × dose |
|---|
| 1 | 50 % | 0.50 |
| 2 | 75 % | 0.75 |
| 3 | 88 % | 0.88 |
| 4 | 94 % | 0.94 |
| 5 | 97 % | 0.97 |
| 6 | 98 % | 0.98 |
This is why a four-week step interval is approximately, but not exactly, steady state.
In practice, glycaemic maintenance has a faster and cleaner signal than weight maintenance, particularly with continuous monitoring, which makes the downward search more tractable when glycaemia is the endpoint.
STEP-4 and SURMOUNT-4 evaluated withdrawal rather than dose reduction, which is the limit of the direct evidence on this question.
The caveat is that dose reduction is a clinical decision and this is a description of a search strategy rather than a recommendation.
Glycaemic maintenance gives a faster signal than weight maintenance.
2Adding for future readers: write down what "working" means before you start. – loss_on_drying 8 months ago add a comment