What is the reported incidence of constipation on cagrilintide in SURMOUNT-4?

What I am working with: constipation · cagrilintide · SURMOUNT-4.

I have read the primary source rather than the summary, which has left me with more questions.

I understand the headline. I do not understand the footnotes, and the footnotes look important.

What can I legitimately conclude from this figure?

Concretely, the mechanism explains the pattern. Delayed gastric emptying plus central appetite suppression produces early satiety, and early satiety plus a slowed transit produces exactly the symptom cluster people report.

Injection-site reactions are more often diluent-related than peptide-related. Benzyl alcohol sensitivity is uncommon but real, and it presents as a consistent local reaction at every site with a preserved diluent and no reaction with an unpreserved one — which is a straightforward thing to establish. Injection depth is the other common cause: intradermal placement stings and welts, subcutaneous placement usually does not.

The gallbladder signal tracks the rate of weight loss more than it tracks the drug. Rapid mobilisation of adipose tissue increases biliary cholesterol saturation and reduces gallbladder motility; that combination is lithogenic whether the loss came from a drug, a very-low-energy diet or bariatric surgery. The drug contribution on top of that is present but smaller than the rate contribution.

The prescribing information for each agent lists adverse reaction frequencies against placebo in a table, and reading that table is more informative than reading a hundred anecdotes, because it has a denominator.

Fix the fixable causes first — fluid, electrolytes, sleep, intake — before concluding that the compound is responsible.

More usefully, the honest framing is that this is very common, usually self-limiting, and occasionally the presentation of something that is not self-limiting at all — and the differentiating features are specific enough to be worth knowing.

Distinguishing an injection-site nodule from an infection: a nodule is firm, non-tender or mildly tender, not warm, not expanding, and appears within a day or two. Cellulitis is warm, tender, expanding, and often accompanied by systemic features. A sterile abscess sits between the two and is fluctuant. Warmth plus expansion plus fever is the combination that stops being a forum question.

Mechanically, vomiting matters mostly through its consequences. Loss of gastric fluid depletes sodium, chloride and potassium, and hypokalaemia presents as exactly the fatigue and cramping people attribute to the drug. Persistent vomiting also makes a renal panel uninterpretable, because a pre-renal picture looks like renal impairment.

SURMOUNT-1 reported gastrointestinal events as the most frequent adverse events, mostly mild to moderate and mostly during escalation, with discontinuation for adverse events in the single digits per cent[1].

One qualification — reported incidence in a monitored trial population is a lower bound on what happens in an unmonitored one, because trial participants were escalated to protocol and supported through it.

If the timing does not fit the escalation, look for another explanation before settling on the drug.

edited 18 Aug 2024 by harriet_lonsdale — expanded the table to cover the lower concentration

Timing is the most useful diagnostic feature here and it is the one most often omitted from the question.

Constipation outlasts the nausea because it has two causes and only one of them resolves. Gastric emptying accommodates over weeks; total intake, and therefore stool volume and the osmotic load reaching the colon, does not recover until intake does. This is why fibre alone can make it worse — you add bulk to a system that is short of water and short of motility.

The pooled gastrointestinal adverse-event rates across the STEP programme and the SURMOUNT programme are reported in the primary publications and in the FDA and EMA assessment reports, and the assessment reports are more useful because they give the placebo-arm rates alongside the active-arm rates in the same table.

The caveat that actually matters: this is pattern recognition from published data, not a clinical assessment of you. Anything severe, persistent or accompanied by systemic features belongs with a clinician the same day.

A symptom diary with dates against dose steps answers most of these questions without anyone needing to guess.

edited 16 Oct 2024 by jonas_ekstrom — clarified the distinction between purity and content

The incidence figures are dose-related but the timing is escalation-related, and conflating the two produces most of the bad advice in this area. Adverse events cluster in the one to two weeks following each dose increase, then decay.

The telogen effluvium timing signature is the diagnostic feature: hair enters the shedding phase two to four months after the insult, so shedding that starts at month three of rapid loss and peaks around month four to five is the expected pattern. Shedding that starts in week two is not telogen effluvium and warrants a different question. In either case the follicle is not destroyed and regrowth is the rule.

Telogen effluvium following substantial weight loss is documented independently of any pharmacotherapy, which is the cleanest argument that the rate of loss rather than the agent is the primary driver.

The limitation of the timing heuristic is that it works well for common events and poorly for rare ones, which are precisely the ones that matter most.

Write down in advance which symptoms mean stop and seek care. It is a short list and it is much easier to write when you are well.