PT-141, Melanotan II and kisspeptin for sex: what the 2026 peptide review shows

Peptides are having a moment, and sexual health is one of the places they are sold hardest: PT-141 nasal sprays, Melanotan II pens and kisspeptin vials are marketed online for erections and libido. On 6 November 2026, The Journal of Sexual Medicine published a systematic review of the human evidence. It found 12 studies with 372 men in total, covering four peptides: the melanocortin agonists PT-141 (bremelanotide) and Melanotan II, kisspeptin and oxytocin.

Short answer: the melanocortin peptides can trigger erections in small laboratory studies, at the cost of frequent nausea, and the largest positive trial in men carries a 2023 expression of concern from the journal that published it. Kisspeptin looks promising for low sexual desire in one 32-man trial that used a hospital infusion, not the injections sold online. Oxytocin results are mixed. None of these peptides is approved for sexual problems in men in the UK or the US, and products sold as research chemicals are not approved medicines. The review's own conclusion is that more studies are needed before they can be used in routine practice.

What the review covered

The authors searched PubMed, Scopus and Web of Science for randomised trials, crossover studies, prospective clinical studies and experimental physiological studies of peptide treatments in adult men. They concluded that melanocortin receptor agonists have the strongest evidence for erections and that kisspeptin is a promising emerging option for sexual desire and hormone signalling. They also listed the weaknesses: small samples, mixed populations, short follow-up and a lack of comparative studies.

PT-141 and Melanotan II

Melanotan II was first developed as a tanning agent. In a 1998 University of Arizona crossover study, 10 men with erectile dysfunction of no known physical cause received a single injection of Melanotan II or placebo on separate days; 8 of the 10 developed erections, with an average of 38.0 minutes of tip rigidity greater than 80% against 3.0 minutes on placebo. Nausea, stretching and yawning, and reduced appetite were more common on the drug. A 2000 study of 10 men with physical risk factors reported erections after 12 of 19 Melanotan II injections and 1 of 21 placebo doses, and 4 of the 19 injections were associated with severe nausea.

PT-141, now called bremelanotide, is a related compound. The largest trial in men, published in 2008, randomised 342 men whose erectile dysfunction had not responded to sildenafil to a 10 mg bremelanotide nasal spray or placebo, and reported a positive result in 33.5% against 8.5%, with more side effects on the drug. In January 2023 The Journal of Urology published an expression of concern about that paper. Results that rest mainly on it should be treated with caution.

In 2019 FDA approved bremelanotide as Vyleesi, a 1.75 mg injection, for premenopausal women with acquired, generalised low sexual desire that causes distress. The label states that it is not indicated in men or to enhance sexual performance. In the phase 3 trials, 40% of patients had nausea, 13% needed anti-nausea medicine and 8% stopped because of nausea. Blood pressure goes up and heart rate goes down after each dose, and these changes usually go away within 12 hours. It must not be used with uncontrolled high blood pressure or known cardiovascular disease. Darkening of the skin, including the face, gums and breasts, was reported by 1% of patients who received up to 8 doses a month. The label says not to use more than one dose in 24 hours and not to use more than 8 doses a month.

Melanotan II has no approval in the UK, the US or South Africa. A 2017 dermatology review of unregulated melanotan use describes case reports of changes in existing moles and new atypical moles, and four case reports of melanoma arising in moles during or shortly after use; it notes that conclusive evidence of cause is lacking and that several national health bodies have issued warnings.

Kisspeptin

Kisspeptin is a natural hormone that sits at the top of the reproductive hormone chain. In a 2023 Imperial College London crossover trial, 37 men with hypoactive sexual desire disorder were randomised and 32 completed it. Each received a 75-minute intravenous infusion of kisspeptin-54 and, on another visit, a placebo infusion while watching sexual videos in a brain scanner. Kisspeptin changed activity in brain areas linked to sexual processing, increased penile tumescence by up to 56% more than placebo and increased reported happiness about sex. This was a single supervised dose in a research unit, measured over hours.

The hospital trial used kisspeptin-54. Kisspeptin-10 is a shorter fragment and a different compound. FDA lists kisspeptin-10 in category 2 of its compounding nominations, the group of bulk drug substances that raise significant safety risks. The World Anti-Doping Agency prohibits kisspeptin and its agonist analogues in sport at all times.

Oxytocin

Oxytocin, the bonding hormone, showed mixed results in the review: possible benefits for orgasm intensity, sexual satisfaction and partner interaction, but no consistent improvement in erections, time to ejaculation or semen quality.

Where the law stands

The US Department of Health and Human Services notice of 30 October 2026 says the department does not intend to take enforcement action, under stated conditions, when a state-licensed pharmacy, a federal facility or a licensed physician compounds six peptides only: BPC-157, TB-500, epitalon, MOTS-c, KPV and Semax. The notice says the policy creates no rights and is not binding. PT-141, Melanotan II, kisspeptin and oxytocin are not among them.

Our view

• Do not inject or spray research peptides for erections or libido. The best human data are small, short and partly in doubt, and the products sold online are not approved medicines.
• Bremelanotide is a real medicine with real side effects, but it is licensed in the US for premenopausal women, not men.
• Kisspeptin is the one to watch. A properly sized trial of a usable form in men with low desire would be news; a vial from a peptide website is not.
• Erection problems that keep happening can be a sign of a treatable condition such as high blood pressure, high cholesterol, diabetes or depression, so they are worth a proper check with a doctor.

South African rules

SAHPRA names Melanotan II and PT-141 among examples of illegally marketed peptides sold through online platforms, social media, gyms, wellness centres and informal suppliers. Under the Medicines and Related Substances Act 101 of 1965, any product intended to treat, prevent or alter bodily functions must be registered with SAHPRA before it can be sold. SAHPRA warns against self-administration without medical supervision, especially of products bought online or from unverified sources. See a doctor about erection problems that keep happening, and report side effects to adr@sahpra.org.za.

FAQ

Is PT-141 the same as bremelanotide?

Yes. PT-141 was the development code for bremelanotide. The approved US product, Vyleesi, is a 1.75 mg injection for premenopausal women with low sexual desire, and its label says it is not indicated in men.

Does Melanotan II work for erections?

Two small studies from 1998 and 2000, each with 10 men, found it could trigger erections, with frequent nausea. It is an unlicensed product linked in case reports to changes in moles, and it should not be used.

Can kisspeptin raise libido?

One 2023 trial in 32 men with low sexual desire found a single hospital infusion of kisspeptin-54 changed brain responses and increased arousal measures. That has not been shown for kisspeptin-10, a shorter fragment and a different compound.

Are these peptides banned in sport?

Kisspeptin and its agonist analogues are on the World Anti-Doping Agency's 2026 prohibited list, in section S2, prohibited at all times. Athletes should check any peptide with their anti-doping organisation.