Coming off: what the pharmacology permits

The vocabulary of tapering arrived in this field from pharmacology where it means something specific: reducing a dose gradually to avoid a withdrawal syndrome produced by neuroadaptation. Incretin receptor agonists produce no such syndrome. There is no dependence, no rebound phenomenon in the pharmacological sense, and no cluster of symptoms on cessation beyond the return of appetite and the reversal of the metabolic effects. A drug with a seven-day half-life also tapers itself: concentrations fall by half a week after the last injection and to a few per cent within a month, whether the reduction was planned or not.

Intermittent schedules: the evidence, stated in full

This section is short because the evidence is. The Journal has searched the trial registries and the published literature for any randomised comparison of an intermittent schedule against a standard weekly schedule for any GLP-1 receptor agonist or dual agonist, at any dose, for any indication. We have found none. We have also found no observational cohort large enough to characterise outcomes on such a schedule with the standard confounders addressed.

What exists is dose-ranging data from the phase 2 programmes, which establishes that lower average exposures produce smaller weight effects, and pharmacokinetic modelling, which establishes what average exposure and what peak-to-trough ratio a given interval would produce. Neither tells you whether a fortnightly schedule maintains weight in somebody who has already lost it, which is the question actually being asked.

An absence of evidence is not evidence of harm and the Journal does not present it as such. It is, however, the entire evidentiary position, and readers encountering confident protocols for intermittent use should know that the confidence is not coming from data. Nothing in this section is advice, and the compounds sold for research use only that appear in some of these protocols are not approved for human use.

The case for tapering, stated as fairly as we can

There is no withdrawal syndrome from these agents, no dependence, and no pharmacological reason to reduce gradually rather than to stop. A seven-day half-life produces its own taper: concentrations halve within a week and fall to a few per cent within a month regardless of intent. On the pharmacology alone, a planned taper accomplishes nothing that stopping does not.

The behavioural argument is different and better. Appetite returns over weeks. A person whose dose is reduced in steps experiences that return in stages, while continuing to have some pharmacological support, and has a window in which to establish eating patterns that will have to hold without the drug. A person who stops outright experiences the same return without that window. Whether the window produces better outcomes is an empirical question that has not been asked in a trial.

The Journal’s position is that the behavioural argument is worth making on its own terms and worth not dressing in pharmacological clothing. What a taper cannot do is prevent regain, since the withdrawal trials establish that ongoing exposure is what holds the weight. Presenting a taper as a way of stopping without regaining is a claim the evidence does not support in any form.

The first six weeks after the last injection

Exposure falls on a predictable schedule. A week after a final weekly injection roughly half the steady-state concentration remains; at two weeks a quarter; at four weeks a few per cent. Appetite returns along a curve that lags the concentration curve somewhat, and delayed gastric emptying resolves over a similar interval, so the sensation of early fullness that has been governing meal size for months disappears over about a month.

What people report, and the Journal reports it as report rather than as measurement, is that the appetite return is experienced as abrupt rather than gradual — as a threshold being crossed somewhere in the third or fourth week rather than as a smooth ramp. That is consistent with a non-linear relationship between receptor occupancy and the perceived effect, which is what the dose-response data would predict, and it is not consistent with the exposure curve alone.

Glycaemic parameters follow their own timescale. Fasting glucose responds within days to weeks; HbA1c, which reflects the preceding three months with the recent weeks weighted most heavily, will not show the full consequence of stopping for a full quarter. A panel drawn four weeks after cessation will understate the change, and this is a specific and common misreading. In the trial population with type 2 diabetes, where glycaemic control was a co-primary concern, the treatment effect on HbA1c was of the order of one and a half percentage points, which is the scale of what a cessation eventually undoes.¹

What would settle the maintenance question

The Journal’s position is that three trials would resolve almost everything currently argued about in this area, and that all three are straightforward. The first is a dose-reduction design: after a lead-in to target, randomise to full dose, one step down, two steps down, or placebo, and follow for a year with weight as the primary endpoint. It would establish the shape of the descending dose-response curve and would cost a fraction of a pivotal programme.

The second is an interval design: after a lead-in, randomise to weekly, fortnightly and three-weekly administration at the same nominal dose. It would answer the intermittent-schedule question directly and would settle whether the exposure pattern matters independently of average exposure.

The third is a taper design: randomise abrupt cessation against a stepped reduction over twelve weeks, with appetite, eating behaviour and weight measured for a year afterwards. It would test the only argument for tapering that is worth testing.

None of the three is under way as far as the Journal can establish. Readers who know otherwise should write to letters@compoundjournal.com; a registered protocol for any of them would be news in this department.

How the Journal reports a regain figure

Four things accompany every regain number in these pages. Which withdrawal design it comes from, because an off-treatment extension and a randomised placebo switch are different experiments. Whether the lifestyle intervention continued in the arm being described. What the denominator is — regain as a percentage of body weight, as a percentage of the weight lost, or as a final position relative to original baseline, three quantities that are routinely quoted interchangeably. And the follow-up duration, because the regain curve decelerates and a figure at six months is not a figure at a year.

The third of those is where most of the misreporting happens. A statement that participants regained two-thirds is a proportion of loss; a statement that they regained eleven per cent is a proportion of body weight; a statement that they finished 5.6 per cent below baseline is a final position. All three can describe the same arm and they are not interchangeable.

Where a source we are quoting has not stated its denominator, we say that rather than inferring it. Readers who find a regain figure in these pages without its design and its denominator have found an error, and the standards desk would like to hear about it at standards@compoundjournal.com.

What this piece is not

This is reporting on a body of trial evidence and it is not advice about whether or how to stop taking a medicine. The decision to discontinue an agent prescribed for glycaemic control, cardiovascular risk or kidney disease is materially different from the decision to discontinue one prescribed for weight, and in every case it belongs with a clinician who has seen the person and knows why the drug was started.

Two further notes. Compounds sold for research use only are not approved for human use in any jurisdiction, and nothing here should be read as guidance about using them or about stopping their use. And where this piece describes what clinicians report doing about maintenance dosing, that is description of practice and not a schedule anybody should adopt from a magazine.

The Journal takes correspondence on this subject at letters@compoundjournal.com and factual challenges at standards@compoundjournal.com. Letters describing a personal experience of stopping are read with attention and are published, where they are published, as accounts rather than as evidence — a distinction this department tries hard to preserve in both directions.

What the shortage years demonstrated, at a scale no trial will ever match, is that this class is now being stopped and restarted routinely by circumstance rather than by decision. That is the discontinuation that actually happens, and there is no literature on it at all. The Journal regards documenting it as reporting rather than research, and will keep doing so.