The answer so far

Melanotan II and PT-141 are different substances. Small studies found short-term changes in erections and, in one study, reported desire after Melanotan II; they also reported nausea. PT-141 is bremelanotide, a prescription medicine with a specific US indication for some premenopausal women. Neither a shared biological pathway nor an online label makes the products interchangeable.23

On this page
  1. Why would a tanning peptide affect sexual response?
  2. What did the first small study measure?
  3. What did the second study find?
  4. Do erections and desire mean the same thing?
  5. Is PT-141 the same as Melanotan II?
  6. How substantial was the effect of the prescription medicine?
  7. What about an online product or combining products?
  8. When is it sensible to seek help?
  9. Sources
LINKED BUILDING BLOCKSAmino acids joined into a chainSequence and structure both matter
Conceptual schematic. Simplified and not to scale; not a scan, microscopy image or validated simulation.

Why would a tanning peptide affect sexual response?

An unexpected effect in early pigmentation research led scientists to investigate whether Melanotan II could influence sexual response. It acts on a family of signalling switches called melanocortin receptors; those signals are involved in more than skin pigmentation. That does not mean every response follows the same pathway or that a tanning product is a tested sexual-health treatment. See the Melanotan II overview and why darker skin is not sunscreen.12

Three questions, different evidenceRelated signals do not make these products or outcomes interchangeable.
  • Melanotan II: erectionTwo small crossover studies in men measured short-term responses, with nausea reported.
  • Melanotan II: desireThe 2000 study also asked ten men about desire; it did not establish treatment for a desire disorder.
  • Bremelanotide: desire and distressTwo larger trials studied a different medicine in premenopausal women with a specific diagnosis.
  • Satisfaction and safetyThe bremelanotide trials did not show a significant difference in satisfying events; nausea was common.

What did the first small study measure?

In 1998, researchers compared Melanotan II with placebo in ten men with erectile difficulties for which no organic cause had been identified. In a crossover study, participants received each treatment at separate times; the researchers monitored responses for six hours. They reported increased erection measurements after Melanotan II. More nausea, yawning and reduced appetite were reported than after placebo. This was a very small, short experiment, not a study of longer-term treatment or everyday sexual satisfaction.12

What did the second study find?

In a separate 2000 crossover study, ten men with erectile difficulties and physical risk factors received Melanotan II and placebo on separate occasions. A participant-reported erection followed 12 of 19 active administrations and one of 21 placebo administrations. These numbers count administrations, not 40 different people; one allocation error contributed to the unequal counts. Severe nausea was reported after four of the 19 active administrations. The study also measured rigidity and asked about desire. Six-hour observation in ten people cannot establish durability, uncommon harms or who would benefit outside the study.2

Do erections and desire mean the same thing?

Sexual desire is an interest in sexual activity; arousal can include mental and physical responses, and an erection is one physical response. They can overlap, but one does not automatically prove the others or predict satisfaction. The 2000 Melanotan II report described higher self-reported desire as well as erection measurements in its small male sample. It does not establish effects for all people, for women or for a diagnosed desire disorder. A separate bremelanotide trial asked a different question in a different population.24

Is PT-141 the same as Melanotan II?

PT-141 is another name for bremelanotide, a different melanocortin medicine, not another name for Melanotan II. In the United States the prescription product Vyleesi is indicated for premenopausal women with acquired, generalised hypoactive sexual desire disorder: distressing low desire that began after a time without the problem and occurs across situations, when the specified medical, relationship and medicine-related causes are excluded. The US label does not indicate it for men, postmenopausal women or enhancement of sexual performance. That indication does not establish approval elsewhere or make a vial labelled PT-141 the authorised product. For a fuller practical introduction, see the bremelanotide profile.34

How substantial was the effect of the prescription medicine?

In two sponsor-funded, 24-week placebo-controlled trials of prescription bremelanotide, participants reported a greater average improvement in desire and related distress scores than placebo; the difference in number of satisfying sexual events was not statistically significant. Nausea was reported by 40.0% of participants receiving bremelanotide and 1.3% receiving placebo. The US label also warns of temporary blood-pressure increases, and says not to use Vyleesi with uncontrolled high blood pressure or known cardiovascular disease. These results and precautions concern the studied prescription product, not a measured risk or benefit for an online Melanotan II vial. See the trial guide for the actual score changes and early discontinuations.34

What about an online product or combining products?

The label on an online product cannot by itself establish its identity, amount or sterility. In 2026, Australia’s TGA found variable amounts when testing five bottles of one product labelled Melanotan II; this was not a survey of every product. The small studies above also do not establish the effects or safety of combining Melanotan II with bremelanotide or erectile-dysfunction medicines. For how far a laboratory document can go, see what a certificate of analysis can show.5

When is it sensible to seek help?

Occasional changes in desire or erections are common and do not automatically mean illness. If a change is persistent or distressing, a clinician or sexual-health service can discuss possible physical, emotional, relationship and medicine-related factors without assuming one cause. An erection lasting more than three to four hours needs emergency assessment; NHS guidance advises earlier emergency help for a painful erection lasting over one hour in someone with sickle-cell disease. Bring details of any medicines or products used. See the linked NHS guidance for the UK context and use local emergency services elsewhere.67

Sources, kept close.

Selected supporting sources; this is not a complete literature review.

  1. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover studyJournal of Urology / PubMed · Small double-blind placebo-controlled crossover study; United States; 1998Access checked 2026-11-05 · Ten men, placebo-controlled crossover, short monitoring; abstract and published contemporaneous commentary reviewed, not the full original paper.
  2. Melanotan II, penile erection and sexual desire in men with organic erectile dysfunctionUrology / PubMed · Primary double-blind crossover trial; US; 2000Access checked 2026-11-05 · Ten men; six-hour observation; 19 active and 21 placebo administrations, not unique participants. One allocation error explained by publisher full-text preview.
  3. Vyleesi (bremelanotide): US prescribing information, revised October 2026US Food and Drug Administration · US product label; revised October 2026Access checked 2026-11-06 · Revised October 2026. US prescription product and defined premenopausal HSDD indication; includes trial results, contraindications, interactions and storage. Not a Melanotan II label or evidence for another product.
  4. Bremelanotide for hypoactive sexual desire disorder: two randomized phase 3 trialsObstetrics & Gynecology / PubMed Central · Sponsor-funded randomized controlled trials; 2019Access checked 2026-11-06 · Two sponsor-funded and sponsor-involved, 24-week placebo-controlled trials in selected premenopausal women with HSDD, most white and enrolled in the US. Outcomes include desire and distress scales, satisfying events and adverse events; early discontinuation and missing data limit interpretation. Not Melanotan II.
  5. Melanotan II tanning peptide products found to be inconsistently dosedTherapeutic Goods Administration · Official product safety alert and laboratory testing; Australia; 17 August 2026Accessed 2026-11-04
  6. Erection problems (erectile dysfunction)NHS · Public health guidance; UK; reviewed July 2023Access checked 2026-11-05 · General assessment context; not a Melanotan II study.
  7. Priapism (painful erections)NHS · Public health urgent-care guidance; UK; reviewed December 2023Access checked 2026-11-05 · Urgency guidance and sickle-cell exception; use local emergency services outside the UK.

The next useful question.

Substance profile

Melanotan II.

Why Melanotan II’s tanning and sexual-function marketing should be treated as an unapproved-drug and product-quality question.

3 min read