Setmelanotide side effects and risks

Reported side effects

• Darkening skin: POMC/LEPR/PCSK1: 78% of 27; BBS: 63% of 43; hypothalamic obesity: 58% vs 10% placebo., mild. Skin darkening often fades after stopping; changing moles still need review. (source)
• Injection-site reactions: 96% of 27 in genetic deficiency trials; 51% of 43 in BBS; 67% of 12 children ages 2–5., mild. Rotate sites and check persistent painful, hot or spreading redness. (source)
• Nausea: Genetic deficiency 56%; BBS 26%; hypothalamic obesity 55% vs 25% placebo., moderate. Dose escalation may need to pause or step back for intolerance. (source)
• Vomiting: Genetic deficiency 30%; BBS 19%; hypothalamic obesity 38% vs 19%; ages 2–5: 58%., moderate. Persistent vomiting needs prompt review, especially with adrenal insufficiency or diabetes insipidus. (source)
• Headache: Genetic deficiency 41%; hypothalamic obesity 37% vs 31% placebo., mild (source)
• Diarrhea: Genetic deficiency 37%; BBS 14%; ages 2–5: 25%., moderate. Check hydration and sodium risk when symptoms persist. (source)
• Constipation: Genetic deficiency 11%; hypothalamic obesity 12% vs 6% placebo., mild (source)
• New or darker moles: Genetic deficiency 19%; BBS 14%; hypothalamic obesity 15% vs 6% placebo; ages 2–5: 33%., moderate. Arrange a skin review for new or changing pigmented lesions. (source)
• Spontaneous erections: Genetic deficiency 23% of 13 males; BBS 25% of 20 males. Hypothalamic obesity label reports 7% vs 4% overall., moderate. An erection lasting more than 4 hours is an emergency. (source)
• Depression: 26% of 27 in the open label genetic deficiency safety cohort., serious. Report new or worsening depression promptly; prescriber may stop treatment. (source)
• Suicidal thoughts: The reported 11% concerns a 27 person cohort in the dossier. It is not an all patient incidence. Monitor new or worsening depression and suicidal thoughts., serious. Seek emergency help for suicidal thoughts or intent. (source)
• Acute adrenal insufficiency: In acquired hypothalamic obesity with secondary adrenal insufficiency: serious events 5% active vs 0% placebo., serious. Urgent care for severe weakness, persistent vomiting, fainting or low blood pressure. (source)
• Low or high sodium: In hypothalamic obesity with diabetes insipidus: low sodium 6% vs 2%; high sodium 5% vs 4%, active vs placebo., serious. Confusion, severe drowsiness or seizures need emergency care. (source)
• Severe allergic reaction: Anaphylaxis is reported after marketing; its frequency cannot be estimated., serious. Stop and get emergency help for breathing trouble, swelling or fainting. (source)

Stop and get help if

• Trouble breathing, swelling of lips or tongue, or fainting after injection: Stop injections and get emergency care for possible anaphylaxis.
• Erection lasting longer than 4 hours: Get emergency care now to prevent permanent injury.
• Suicidal thoughts, intent or severe new mood changes: Get urgent mental-health help; call emergency services for immediate danger.
• Severe weakness, persistent vomiting, fainting or very low blood pressure: With adrenal insufficiency, follow the prescribed emergency steroid plan and get emergency care.
• Confusion, severe drowsiness, seizures or severe headache with fluid changes: Get emergency care for possible dangerous sodium imbalance.
• New or rapidly changing mole, bleeding pigmented spot or unusual dark lesion: Arrange prompt clinical skin assessment; do not assume every change is harmless tanning.
• Low blood sugar that does not recover, confusion or collapse: Get urgent care for persistent low glucose; emergency help is needed for collapse or impaired awareness.

Who should avoid it

• pregnant: Label says discontinue when pregnancy is recognized unless benefits outweigh fetal risks; human pregnancy data are absent.
• breastfeeding: Use while breastfeeding is not recommended by the label; human milk and infant safety data are absent.
• tryingToConceive: This is a precaution. Discuss stopping before trying to conceive; an evidence-based washout interval is unknown.
• under18: This is an app rule; FDA approval includes ages ≥2 for genetic obesity and ≥4 for acquired hypothalamic obesity.
• melanomaOrAtypicalMoles: The US label calls for skin examinations before and during treatment and monitoring of pigmented lesions. Prior serious hypersensitivity is the formal contraindication.
• eatingDisorderHistory: This is a precautionary app rule, not a labeled contraindication.
• other: Prior serious allergy to setmelanotide or its ingredients is the labeled contraindication. Anaphylaxis has been reported.
• depressionOrSuicidalThoughts: Mood symptoms and suicidal thoughts may occur. Prior depression may raise recurrence risk; monitor during treatment.
• kidneyDisease: Severe kidney impairment needs a lower genetic-obesity dose; acquired hypothalamic obesity use is not recommended. Avoid in end-stage kidney disease.
• other: US label: not recommended at eGFR <15, or acquired hypothalamic obesity with eGFR 15–29. EU has a different kidney-impairment schedule.
• other: Acquired hypothalamic obesity with secondary adrenal insufficiency: serious acute adrenal insufficiency occurred in 5% active versus 0% placebo.
• other: Central diabetes insipidus can lead to dangerous sodium changes. Monitor sodium as fluid intake or hydration changes.
• diabetes: Reduced food intake may lower insulin needs. One insulin-treated patient had repeated glucose <50 mg/dL.
• liverDisease: EU label says do not administer with liver impairment. US label says effects on drug levels are unknown.
• testedAthlete: Setmelanotide is not named on the 2026 list. Confirm the product with the athlete’s anti-doping body; no drug-specific ruling was found.

Interactions

• Insulin and sulfonylureas: Less food and weight loss may lower dose needs. Hypoglycemia occurred with insulin in one published case; no formal interaction trial exists.
• Desmopressin for central diabetes insipidus: In hypothalamic obesity, fluid intake changes may alter sodium control. Monitor sodium and adjust diabetes-insipidus medicines when needed.
• Glucocorticoid replacement: Vomiting can prevent steroid absorption in adrenal insufficiency. Review sick-day dosing and emergency steroid plans with the endocrine team.
• Other melanocortin agonists: Same-pathway combination data are absent. Added nausea, pigmentation or prolonged erections are plausible; do not assume selective MC4R action prevents them.
• GLP-1 and other appetite-lowering medicines: TRANSCEND allowed stable background GLP-1 use; no dedicated combination trial was found. Added nausea and reduced intake may affect hydration and glucose control.
• Oral medicines and anticoagulants: No clinical interaction studies were done. A GLP-1-like delayed-stomach-emptying interaction or specific anticoagulant effect has not been established.

Product quality risks

• No independent setmelanotide-specific survey of online vial purity, sterility or dose accuracy was located.
• General FDA compounding evidence shows risks of contamination and too much or too little active ingredient; no setmelanotide-specific rate is known.
• An online powder or pen is not established as equivalent to the approved 10 mg/mL vial.
• A purity percentage alone cannot show identity, milligrams per vial, sterility or bacterial-toxin levels.