PT-141 (Bremelanotide): Research, Mechanism, and Clinical Evidence for Sexual Function

What it is

PT-141 began as a side effect. Researchers testing melanotan II, a synthetic version of the skin-darkening hormone alpha-MSH, noticed that male volunteers were getting erections. They stripped the tanning activity down and kept the sexual one, and the result, bremelanotide, went through drug development as a peptide that acts on desire in the brain.

The FDA approved it in 2019 as Vyleesi, an on-demand injection for premenopausal women with hypoactive sexual desire disorder, meaning persistent low desire that causes distress and is not explained by another condition or a relationship problem. It is one of the few peptides on this site with a full approval and the trial record that comes with it.

What it is studied for

Low sexual desire in women, the approved use. Erectile dysfunction and desire in men, in earlier studies that did not lead to an approval. Female arousal disorder, in early trials of a nasal version.

What the evidence actually shows

In humans

The RECONNECT program ran two identical Phase III trials, about 1,200 premenopausal women with low desire in total, for 24 weeks. Women on bremelanotide reported greater increases in desire and greater decreases in distress about it than women on placebo. The effects were statistically clear and modest in size; the drug does not create desire from nothing, it raises it somewhat in women who want it raised (Kingsberg et al., 2019).

Earlier, smaller studies with a nasal spray found that women with arousal disorder reported more satisfying sexual events on bremelanotide than placebo (Safarinejad, 2008), and that men with erectile dysfunction, including men who did not respond well to Viagra-type drugs, had better erections (Molinoff et al., 2003). The nasal route was dropped because it pushed blood pressure up too much, and the men’s program was not pursued to approval.

From user reports

Men describe stronger desire and firmer erections starting one to two hours after a dose and lasting several hours, sometimes into the next day. Women describe the same rise in interest. Nausea is the constant complaint, and flushing and a darkening of moles or freckles come up with repeated use.

How it works

Bremelanotide activates the melanocortin-4 receptor in the hypothalamus, part of the brain’s circuitry for sexual motivation, and sets off signaling through dopamine and oxytocin pathways (Pfaus et al., 2013). That is the difference from Viagra and its relatives, which act on blood vessels in the genitals and do nothing for desire. PT-141 works upstream, on wanting, in both sexes. Because it still touches other melanocortin receptors, it can also darken skin and reduce appetite, the same family of effects as melanotan II.

How it is used

Vyleesi is 1.75 mg under the skin of the belly or thigh at least 45 minutes before sex, no more than one dose in 24 hours and no more than eight a month. Off-label, men use 1 to 2 mg the same way; research-vendor product is mixed with bacteriostatic water and refrigerated. See the storage guide.

Side effects and unknowns

From the trials: nausea in about 40% of women, worst with the first dose and often fading; flushing, headache, injection-site reactions, and vomiting in a smaller share. Blood pressure rises by a few points for several hours after each dose, and heart rate falls slightly, which is why the label limits use to one dose a day and eight a month and rules it out for anyone with uncontrolled high blood pressure or heart disease. With repeated use, skin, gums, and existing moles can darken, more so in people with darker skin.

The unknowns: long-term use beyond the trials, use in men at the doses they choose, and the cardiovascular effect of frequent dosing outside the label’s limits. See the safety guide.

How it compares

• Viagra, Cialis, and relatives: act on blood flow, not desire; work for erectile dysfunction, do nothing for low libido. PT-141 is the reverse and can be used alongside them.
• Melanotan II: the parent molecule, sold for tanning, with the same sexual effect and more of the nausea and skin darkening; no approval.
• Kisspeptin-10: raises reproductive hormones and has been studied for sexual brain responses in men; no approval.
• Flibanserin (Addyi): the other approved drug for low desire in women, a daily pill acting on serotonin, with an alcohol warning.

Legal status

FDA approved as Vyleesi for premenopausal women with hypoactive sexual desire disorder, prescription only. Off-label use in men and postmenopausal women is legal with a prescription. Also sold as a research chemical. Not on the WADA Prohibited List.

Bottom line

PT-141 is an approved drug that does something no pill does: raise sexual desire itself, in both sexes, through the brain. The effect is real and modest, the nausea is common, and the blood pressure limits are there for a reason. It is one of the few peptides here where the evidence and the marketing roughly agree.

References

1. Kingsberg SA, et al. (2019). Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstet Gynecol. PubMed
2. Diamond LE, et al. (2006). An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141), a melanocortin receptor agonist. J Sex Med. PubMed
3. Safarinejad MR. (2008). Evaluation of the safety and efficacy of bremelanotide, a melanocortin receptor agonist, in female subjects with arousal disorder. J Sex Med. PubMed
4. Molinoff PB, et al. (2003). PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. PubMed
5. Pfaus J, et al. (2013). A review of animal and human data on the melanocortin system and sexual function. Eur J Pharmacol. PubMed

See also

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  Kisspeptin-10 is a brain signal that switches on the body's reproductive hormones, studied in human trials for fertility treatment and hormone testing.

• Peptide
  Ipamorelin: What the Evidence Says About This Selective GH Secretagogue

  Ipamorelin is a five-amino-acid peptide that mimics ghrelin to release a pulse of growth hormone, and unlike its predecessors does it without raising cortisol, prolactin, or hunger. Human data: one dosing study and one abandoned surgery trial.

• Peptide
  Selank: Research, Mechanism, and Clinical Evidence for Anxiety and Cognition

  Selank is a seven-amino-acid peptide, a stabilized version of an immune fragment called tuftsin, approved in Russia as a nasal spray for anxiety. Small Russian trials found it worked about as well as a benzodiazepine without the sedation.