What Is PT-141 (Bremelanotide)? How It Works, the Vyleesi Trials, Side Effects and Status in Canada (2026)

Research Guide · 18 min read · Updated October 2026

What PT-141 is

Bremelanotide is a cyclic peptide: its chain is closed into a ring, which makes it much more resistant to breakdown than a linear peptide of the same size. It is chemically almost identical to Melanotan II, differing mainly at one end of the molecule, and is in fact a metabolite of it.

An accidental discovery: from tanning to desire

PT-141’s story starts in the 1980s and 1990s at the University of Arizona, where researchers were developing synthetic versions of alpha-melanocyte-stimulating hormone (α-MSH) to tan the skin and potentially protect against skin cancer. One of those compounds was Melanotan II.

In an early human study of Melanotan II for tanning, volunteers reported an unexpected side effect: spontaneous erections. Follow-up studies by Wessells and colleagues in 2000 confirmed that Melanotan II produced erections in men with erectile dysfunction and increased sexual desire.

Palatin Technologies then developed bremelanotide as a more focused compound for sexual function, aiming to keep the effect on desire while reducing the tanning effect. The name PT-141 comes from Palatin’s compound numbering. For the tanning side of the family, see Melanotan 1 vs Melanotan 2.

How it works: the melanocortin system

The melanocortin system is a set of five receptors (MC1R to MC5R) that respond to hormones derived from a precursor called POMC. Each receptor does something different:

Activation of MC4R in the hypothalamus is thought to increase dopamine release in brain areas linked to motivation and sexual desire, notably the medial preoptic area. That’s why PT-141 is described as acting on the “desire” side of sexual function rather than the mechanical side. The same receptor also regulates appetite, which is why a related MC4R agonist, setmelanotide (Imcivree), is approved for rare genetic forms of obesity.

The melanocortin family tree

PT-141 is one member of a family of compounds built on the same natural hormone. Seeing them side by side explains a lot about how each behaves.

The pattern is that the more a compound activates MC1R, the more it tans; the more it activates MC4R, the more it affects appetite and sexual function. Bremelanotide sits between the two, which is why it has a small pigmentation risk.

Desire and the brain: why a brain-acting drug makes sense

Sexual medicine researchers often describe desire with a “dual control” model: excitatory signals that push toward sexual interest and inhibitory signals that hold it back. On the brain chemistry side, dopamine, melanocortins and noradrenaline are broadly excitatory, while serotonin is broadly inhibitory.

The two drugs approved for HSDD in the US approach that balance from opposite ends. Flibanserin acts on serotonin receptors to reduce inhibition; bremelanotide activates melanocortin receptors to increase excitation. This framework also explains a familiar clinical problem: antidepressants that raise serotonin (SSRIs) commonly reduce desire, a side effect researchers have studied as a target for melanocortin agonists.

None of this makes desire a simple chemical switch. Relationship factors, stress, fatigue, body image and health all shape it, which is why the trial effects of both drugs were modest.

PT-141 vs Viagra: brain vs blood flow

This is the comparison most people search for, and the two drugs work in completely different ways.

Because they act on different systems, researchers have studied PT-141 in men who did not respond to PDE5 inhibitors, and in combination with them.

The men’s program and why it stopped

Palatin’s first goal was erectile dysfunction in men. In the 2000s, an intranasal form of bremelanotide went through phase 2 trials in men with ED, including men who hadn’t responded well to sildenafil, with positive effects on erectile function.

The program stalled around 2007–2008 over blood pressure. The nasal spray caused increases in blood pressure in some participants, raising concerns about cardiovascular risk in a population of men with ED, who frequently have heart disease and high blood pressure. Palatin dropped the nasal route, reformulated bremelanotide as an under-the-skin injection with more predictable absorption, and refocused on women with low desire, where there were few treatment options.

As a result, PT-141 has never been approved for men, anywhere. The men’s data remain phase 2 only.

What HSDD is

Hypoactive sexual desire disorder is a persistent lack of sexual thoughts, fantasies or desire for sexual activity that causes the person marked distress, and that isn’t better explained by another medical condition, a medication, relationship problems or other stressors. The distress part is essential: low desire that doesn’t bother someone is not a disorder.

HSDD is the most commonly reported sexual problem in women in surveys, though estimates vary widely. Its causes are a mix of biological, psychological and relationship factors, which is part of why a single drug was never going to be a complete answer. First-line approaches include addressing contributing medications (antidepressants are a common culprit), treating depression or anxiety, and sex therapy or cognitive-behavioural approaches. For broader context, see Menopause treatment in Canada, since desire changes are common around menopause, a group in which bremelanotide is not approved.

The RECONNECT phase 3 trials

Vyleesi’s approval rested on two identical phase 3 trials, together called RECONNECT, published by Kingsberg and colleagues in Obstetrics & Gynecology in 2019.

An open-label extension reported that the improvements were maintained in women who continued, though open-label data are weaker evidence than the randomized phase.

How trials measure desire

Sexual desire can’t be measured with a blood test, so trials rely on validated questionnaires. Understanding them helps you read the results.

• FSFI desire domain. Two questions from the Female Sexual Function Index asking how often and how strongly a woman felt desire over the past four weeks. Scores run from 1.2 to 6.0.
• FSDS-DAO item 13. One question from the Female Sexual Distress Scale asking how bothered a woman is by low desire. Because HSDD is defined by distress, reducing it is a core goal.
• Satisfying sexual events (SSEs). A diary count of sexual encounters the participant found satisfying. It is concrete but noisy, because it depends on partners, opportunity and circumstances.

Regulators accepted desire and distress as co-primary endpoints for bremelanotide. Critics argued the SSE result matters more to patients; supporters argued that desire, not activity, is what HSDD is about. Both views are reasonable, and it’s worth knowing which measure a claim is based on.

Who was in the trials

The RECONNECT participants were premenopausal women, average age 39, most of them in the US (97%) and most of them white (86%). They had acquired, generalized HSDD, meaning low desire that developed after a period of normal desire and occurred in all situations, not just with one partner. Women whose low desire was better explained by another condition, a medication or relationship problems were not the target population.

That makes the results quite specific. They don’t tell us how bremelanotide performs in postmenopausal women, in men, in women whose low desire is caused by antidepressants, or in populations outside the US.

How big is the effect, really?

This is where honest summaries differ from marketing. Three points put the result in context:

• The desire improvement was modest. On the FSFI desire scale, which runs from 1.2 to 6.0, the difference between bremelanotide and placebo was 0.35 points in the combined analysis (0.30 and 0.42 in the two trials). Statistically clear, but small in absolute terms.
• Placebo responses were substantial, as they typically are in sexual medicine trials. Many women on placebo also improved.
• Satisfying sexual events didn’t increase significantly compared with placebo, a measure that had been the primary endpoint for the earlier HSDD drug, flibanserin.

For some women, a modest improvement in desire and a reduction in distress is meaningful, and the drug gives them an on-demand option without daily dosing or alcohol restrictions. But it isn’t the dramatic “libido peptide” it’s often described as online.

Side effects and safety

The RECONNECT trials and prescribing information give a solid picture of side effects.

Nausea was usually mild to moderate and tended to lessen with repeated use, but it was the main reason women stopped treatment in the trials.

Other important safety points from the label:

• Blood pressure and heart rate: each dose causes a temporary rise in blood pressure and a fall in heart rate, which return to normal within about 12 hours. Bremelanotide is not recommended for people with uncontrolled high blood pressure or known cardiovascular disease.
• Drug interactions: it slows stomach emptying, which can reduce absorption of some oral medicines. Notably, it can significantly reduce blood levels of oral naltrexone.
• Pregnancy: should be stopped if pregnancy is suspected.

A full breakdown is in PT-141 side effects.

Darkening of the skin and gums

Because bremelanotide also activates MC1R, the tanning receptor, about 1% of trial participants developed focal hyperpigmentation: darkened patches on the face, gums or breasts. The risk was higher with daily use for consecutive days, and the darkening didn’t always resolve after stopping. The label limits how often it can be used per month, partly for this reason.

This is the clearest link back to Melanotan II, which was designed to tan. Melanotan II is a far stronger MC1R activator and has been associated with new and changing moles in case reports. See Melanotan II side effects.

PT-141 vs flibanserin vs kisspeptin

Kisspeptin is an interesting newer research direction: small studies at Imperial College London found it increased activity in brain areas linked to sexual arousal in men and women with low desire. We compare all three in Kisspeptin vs hCG vs PT-141.

Status in Canada, the US and elsewhere

• United States: approved by the FDA on June 21, 2019, as Vyleesi, for acquired, generalized HSDD in premenopausal women. Commercial rights have changed hands since launch.
• Canada: not authorized by Health Canada. There is no approved bremelanotide product in Canada, so it cannot be legally prescribed as an approved drug or sold for human use.
• Men: not approved anywhere.
• Research market: PT-141 is sold in Canada as a research reagent for laboratory use only, without health claims. In August 2025, Health Canada named bremelanotide among dozens of unauthorized injectable peptides seized from a seller marketing them for human use, and its April 2026 advisory warned against injecting peptides bought online.

For people in Canada concerned about low desire or erectile dysfunction, the starting point is a family doctor or sexual health clinic, which can look for contributing causes and discuss approved options, including the PDE5 inhibitors for ED. See Erectile dysfunction treatment in Canada.

PT-141 timeline

Five myths about PT-141

“It’s the female Viagra.”

The nickname stuck, but it’s misleading. Viagra improves blood flow; PT-141 acts on desire in the brain. They treat different problems through different systems.

“It works instantly and dramatically.”

In controlled trials the effect on desire was modest, placebo responses were large, and satisfying sexual events did not increase significantly versus placebo.

“It’s approved for men.”

It isn’t, anywhere. The men’s program stopped at phase 2 over blood pressure concerns.

“It’s just a safer Melanotan II.”

Bremelanotide went through phase 3 trials and regulatory review; Melanotan II never did. But they are closely related, share side effects such as nausea and flushing, and both can darken the skin.

“Nasal sprays are the gentler option.”

The nasal form is the one that raised blood pressure concerns, partly because absorption was less predictable. No nasal bremelanotide product is approved.

For researchers

PT-141 is a useful tool for laboratory work on:

• Melanocortin receptor selectivity and signalling (MC1R vs MC3R vs MC4R).
• Comparisons across the melanocortin agonist family: α-MSH, Melanotan I, Melanotan II, bremelanotide and setmelanotide.
• Structure-activity work on cyclic peptides and how ring closure affects stability.
• Central pathways of motivation and reward downstream of MC4R.

TrueLabs supplies PT-141 in 10 mg vials from $45, with batch COAs available in the COA library. Because PT-141 and Melanotan II differ only slightly in structure, identity confirmation by mass spectrometry is the key check: see How to read a peptide COA.

See PT-141 →

FAQ

Related reading

• PT-141 side effects
• Kisspeptin vs hCG vs PT-141
• Melanotan 1 vs Melanotan 2
• Erectile dysfunction treatment in Canada
• Kisspeptin side effects

References

1. Kingsberg SA, Clayton AH, Portman D, et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019;134(5):899–908. PubMed
2. Wessells H, Levine N, Hadley ME, et al. Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II. Int J Impot Res. 2000;12 Suppl 4:S74–S79. PubMed
3. Wessells H, Gralnek D, Dorr R, et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology. 2000;56(4):641–646. PubMed
4. Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996;58(20):1777–1784. PubMed
5. US FDA. Drug Trials Snapshots: Vyleesi. FDA
6. Drugs.com. Vyleesi FDA approval history. Drugs.com
7. Health Canada. Advisory RA-77807: Unauthorized injectable peptide drugs seized and sold by Canada Peptide. August 1, 2025. Recalls and Safety Alerts
8. Health Canada. Think twice before injecting peptides bought online. Public advisory, April 9, 2026. Health Canada

This article summarizes published research and regulatory information for information only and is not medical advice. TrueLabs research compounds are sold for in vitro and laboratory research use only and are not intended for human or veterinary use.