Accepted answer
2 mg a week is 0.286 mg a day averaged out and 104 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 2 mg is which arm it corresponds to: if a programme ran 2 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 2 mg a week a 10 mg vial is 5 weeks and you will need about 11 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.
Answer first: the maintenance dose is the lowest one that holds the result, and finding it is a downward search rather than an upward one.
Maintenance and loss are different endpoints. Loss requires a sustained energy deficit; maintenance requires only that the counter-regulatory drive is offset, and that may need less exposure.
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.
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.
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.
The lowest dose that holds the result is the answer, and it is individual.
7Adding a vote because this deserves more of them. – marta_okonkwo 5 months ago add a comment