Melanotan II side effects and risks

Reported side effects

• Nausea and vomiting: Severe nausea after 4/19 active injections in the organic ED study., moderate (source)
• Yawning, stretching and less appetite: More frequent than placebo in the 10 man trials; exact rates not reported., mild (source)
• Sleepiness and fatigue: Grade II at 0.03 mg/kg in 1/2 pilot participants reaching that dose., moderate (source)
• Flushing or headache: Regulatory warnings and community reports; no reliable population rate., moderate (source)
• New or darker moles: Multiple case reports; no reliable rate., serious (source)
• Melanoma after exposure: Cutaneous and oral cases reported; causation and absolute risk are unknown., serious (source)
• Priapism: Case reports include prolonged erections needing hospital treatment., serious (source)
• Muscle breakdown and kidney injury: Reported after a 6 mg injection; another report describes kidney infarction., serious (source)
• PRES brain syndrome: Case report listed by FDA; frequency unknown., serious (source)

Stop and get help if

• An erection lasting 3–4 hours; with sickle-cell disease, a painful erection lasting over 1 hour.: Get emergency care immediately; delay can permanently damage erections.
• Severe headache, confusion, seizure, vision loss or weakness.: Seek emergency care for possible brain or blood pressure complications.
• Severe muscle pain, cola-colored urine, low urine output or flank pain.: Stop exposure and seek urgent care for muscle or kidney injury.
• A fast-changing, bleeding or irregular mole, or a new mouth lump.: Arrange prompt skin or oral assessment; do not assume it is harmless pigment.
• Trouble breathing, facial swelling, or a hot spreading injection-site rash with fever.: Seek urgent care; breathing difficulty needs emergency help.

Who should avoid it

• melanomaOrAtypicalMoles: Precaution for melanoma history, suspicious lesions or atypical moles. Causation is unproven, but pigment changes can obscure assessment.
• pregnant: No established pregnancy safety or approved use.
• breastfeeding: No human milk or infant safety data were found.
• tryingToConceive: No established reproductive safety for this unapproved compound.
• under18: No controlled pediatric safety evidence or approved use was identified.
• kidneyDisease: Kidney injury, muscle breakdown and kidney infarction have been reported after exposure.
• uncontrolledBloodPressure: Serious systemic toxicity and PRES reports warrant review before any exposure.
• heartCondition: Broad melanocortin activity and systemic toxicity make cardiovascular effects a concern.
• seizureDisorder: A PRES case is reported; neurological safety is inadequately characterized.
• testedAthlete: Falls under WADA S0 for nonapproved drugs.
• other: Precaution: prior priapism or sickle-cell disease raises concern for prolonged erections. This is not a formal melanotan II label.

Interactions

• Other melanocortin agonists: Overlapping receptor effects; no established safe combination. Concurrent PT-141 use appears in a community report.
• Erection medicines: Possible additive prolonged erections. This is a precaution; no direct interaction trial was found.
• UV exposure and sunbeds: UV can damage skin. Tanning is not evidence of protection against skin cancer.
• Anticoagulants and antiplatelets: Injection-site bleeding is a procedural concern; a specific melanotan II drug interaction has not been measured.

Product quality risks

• Vials labeled 10 mg contained 4.32–8.84 mg in a 2015 study. Unknown impurities were 4.1–5.9% in products from two of three online shops.
• A 2024 forensic study identified melanotan II in two submitted vials and reported powder purity of 30%.
• These chemistry studies did not establish sterility, endotoxin safety or consistent nasal spray delivery.
• TGA testing in August 2026 found estimated 22–54 mg across five nasal bottles labeled 30 mg, using their labeled 20 mL volume.