Skin and moles darkening is expected. Not expected: new depression, mood change or suicidal thoughts, and prolonged erections.
Mood changes warrant prompt clinical contact; keep monitoring moles.
A prolonged erection over ~4 hours → emergency. Thoughts of self-harm → urgent help (in the US, call or text 988).
Allergic reaction: hives, swelling of the lips, tongue or throat, wheezing or dizziness can escalate to anaphylaxis within minutes — call 911 immediately. Site infection: spreading redness, heat, swelling, pus or fever is not wait-and-see; an abscess or cellulitis can need drainage or IV antibiotics. Unverified product: grey-market vials are frequently mislabelled or contaminated, so a reaction may be to endotoxin or the wrong contents, not the named compound.
A selective MC4R agonist, and a genuine piece of precision medicine. The leptin-melanocortin pathway regulates hunger; when it is broken upstream by a genetic defect — POMC, PCSK1 or LEPR deficiency — hunger signalling runs unopposed. Setmelanotide restores signalling downstream of the defect by agonising MC4R directly, bypassing the broken component. It works because the specific lesion is known, which is exactly why it does not work as a general obesity drug.
Phase 3 trials in genetically defined obesity syndromes demonstrated substantial weight reduction and, notably, reduction in hunger. Later trials supported expansion to acquired hypothalamic obesity.
FDA-approved as Imcivree, for patients aged 2 and older with obesity due to Bardet-Biedl syndrome or genetically confirmed POMC, PCSK1 or LEPR deficiency; and, following expansion, for acquired hypothalamic obesity in patients aged 4 and older. Prescription-only. Requires genetic confirmation — the approval is tied to the genotype, not to obesity generally.
Skin hyperpigmentation is expected and mechanism-based. Injection-site reactions, nausea. Spontaneous penile erections and sexual adverse events are labelled. Depression and suicidal ideation are labelled and require monitoring. Full ophthalmological and skin examination required before and during treatment.
Imcivree: individualised and titrated up to 3 mg once daily SC, only in genetically confirmed patients. FDA-label.
Reported from clinical trials or FDA labelling as a matter of record. It is not a recommendation, and for unapproved compounds no dose has been shown safe or effective in humans.
Above is what was administered in trials or on FDA labels, reported as fact. We do not convert it into a personal protocol, calculate a dose for your body weight, or tell you what to inject or how to reconstitute it — that decision belongs with a licensed physician. See our editorial policy.
Regulatory status changes. This page reflects our reading of public sources as of July 2026 and should be independently verified before it is relied upon.