Melanotan II and PT-141: chemical cousins, opposite stories

Same origin, different paths

Melanotan II and bremelanotide (PT-141) are analogs of alpha-melanocyte-stimulating hormone (α-MSH) and act on melanocortin receptors¹⁷. The first was tested at the University of Arizona: in a three-volunteer pilot phase 1 study it produced tanning, but also nausea and spontaneous erections¹⁰, and it was later tried in men with erectile dysfunction¹¹. Outside research it became famous as the "tanning peptide"; the second was developed as a medicine for hypoactive sexual desire disorder in premenopausal women and went through controlled trials to FDA approval⁷⁹. Bremelanotide has high affinity for the melanocortin type 4 receptor, thought to be important for sexual function¹².

PT-141: approved, but debated

In the two RECONNECT phase 3 trials (1,267 women), bremelanotide was associated with a +0.35-point increase in desire and a −0.33 reduction in distress vs placebo (both P < .001). Nausea, flushing and headache occurred in at least 10% of participants⁷.

The debate is about effect size. A 2024 analysis noted that 8 of the 11 efficacy outcomes registered on clinicaltrials.gov had not been published; analyzing them, it found "nil to small" effects, and it also questioned the validity of the scales used in the trials⁸.

Melanotan: the evidence is case reports

There are no controlled trials of melanotan for cosmetic use; what exists are case reports and series. A 2017 review described changes in existing moles, new moles (some dysplastic) and four melanoma cases arising during or shortly after use, while noting that conclusive evidence of a link is lacking¹. In a review of 179 patients with eruptive nevi, immunosuppressants, chemotherapy or melanotan accounted for 41% of suspected causes².

Some reports stand out for their speed: eruptive moles and darkening of existing moles 24 hours after a single injection of melanotan II³. In 2025, an oral mucosal melanoma was reported in a 22-year-old woman who had used melanotan II nasal spray for tanning; the authors framed it as a possible risk factor⁴. In 2026, five melanomas in situ were described in a patient who had used tanning beds, melanotan and anabolic hormones¹⁵, and dermatologists warned about melanotan being promoted on social media¹⁶.

Beyond the skin

There are also isolated reports of priapism⁵ after a melanotan injection and kidney infarction most likely attributed to melanotan II⁶; the same paper cites earlier cases of rhabdomyolysis and kidney failure⁶. These are individual cases: they can raise a signal, but they cannot measure the risk.