A melanocortin receptor agonist, sold as Vyleesi, FDA-approved in 2019 for low sexual desire in premenopausal women.
Also called Bremelanotide, Vyleesi, PT-141, Bremelanotide acetate
PT-141 is the research code for bremelanotide, a seven-amino-acid ring-shaped peptide that switches on melanocortin receptors in the brain. Unlike Viagra, which works on blood flow in the penis, bremelanotide acts in the central nervous system, which is why it was developed for desire rather than for erections. In 2019 the FDA approved it as Vyleesi, a 1.75 mg autoinjector for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD).
The approval rests on two 24-week phase 3 trials (RECONNECT) in 1,267 women. Bremelanotide beat placebo on desire and on distress about low desire, but the gains were small: about 0.35 points on a desire score that runs from 1.2 to 6, and no significant difference in the number of satisfying sexual events per month. About 40% of women had nausea, and 18% of women on bremelanotide stopped the trials because of side effects, compared with 2% on placebo.
Online, PT-141 is sold as a research powder and promoted for men with erectile problems and for general libido. Those uses are not approved. The male erectile studies are small, early and from the 2000s, and the largest of them now carries a journal expression of concern. Bremelanotide also raises blood pressure for several hours after each dose and can darken patches of skin with frequent use.
What it binds to, and what happens inside the body after that, step by step.
Bremelanotide activates several melanocortin receptors, most strongly MC1R and MC4R at the approved dose. MC4R is found on neurons across the brain, including the hypothalamus, which is thought to be where its effect on sexual desire comes from, although the FDA label states the exact mechanism in HSDD is unknown. MC1R sits on pigment cells, which explains the skin darkening seen with frequent dosing.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
Two large phase 3 RCTs and a 52-week open-label extension show bremelanotide produces a statistically significant but small improvement in desire and desire-related distress in premenopausal women with HSDD, without increasing the number of satisfying sexual events. Evidence in men is limited to small, early erectile-function trials, and evidence for postmenopausal women, healthy users and long-term frequent dosing is thin.
1,267 premenopausal women with HSDD, 24 weeks
Desire score rose 0.35 points more than placebo (integrated, P<.001) and distress fell 0.33 points more; nausea, flushing and headache each hit 10% or more.
Read the study684 women from RECONNECT, 52-week open-label extension
272 completed; desire scores stayed improved and no new safety signals appeared, with nausea in 40.4% and flushing in 20.6%.
Read the study327 premenopausal women with sexual dysfunction, 12 weeks
At 1.25 or 1.75 mg, satisfying sexual events rose by 0.7 per month versus 0.2 on placebo (p = 0.018).
Read the studyPremenopausal women with BMI over 30, 4 to 16 days
Weight fell 1.3 kg more than placebo over 16 days with about 400 kcal/day less food intake; these were short sponsor-run studies.
Read the study19 men with erectile dysfunction, single-dose crossover
7.5 mg intranasal PT-141 plus 25 mg sildenafil produced a larger erectile response on RigiScan than sildenafil alone.
Read the study342 men with erectile dysfunction not helped by sildenafil
33.5% responded on 10 mg intranasal bremelanotide vs 8.5% on placebo; the journal issued an expression of concern about this paper in 2023.
Read the studyNo preclinical studies are listed as key studies here. The human data above carries the evidence.
These are questions the published research has not answered.
Approved only for premenopausal women with acquired, generalized HSDD. The label says it is not indicated for postmenopausal women, for men, or to enhance sexual performance. AMAG Pharmaceuticals launched it; Palatin took it back in 2020 and sold it to Cosette Pharmaceuticals in December 2023. Bremelanotide is not named on the WADA Prohibited List. Products sold online as 'PT-141' are unregulated research chemicals, not Vyleesi.
How much of PT-141 (Bremelanotide) is left after a single dose
Simple first-order model from the published half-life. Real clearance varies with dose, route, kidney and liver function and formulation. This is not a dosing schedule.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
Viagra relaxes blood vessels in the genitals. Bremelanotide acts on melanocortin receptors in the brain and was approved for low desire, not for arousal or blood flow problems.
In the approval trials the desire score rose about 0.35 points more than placebo on a 1.2 to 6 scale, and the number of satisfying sexual events did not differ from placebo. Some women respond well; the average effect is small.
Small early trials showed better erections on RigiScan and in men who failed sildenafil, but the largest of those papers now has an expression of concern, and the drug was never approved for men.
40% of women in phase 3 had nausea, about 20% had flushing, blood pressure rises after each dose, and frequent dosing darkened skin in over a third of people in one study.
It does activate MC1R and can darken skin, but as uneven patches on the face, gums and breasts, not an even tan, and the patches did not always fade.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Bremelanotide works on desire in the brain while sildenafil-type drugs work on blood flow, so the two are discussed together for men with erectile dysfunction.
EvidenceOne 19-man single-dose crossover study (2005) showed a larger erectile response with the combination. No long-term safety data, and the blood pressure effects of both drugs have not been studied together at scale.
Vyleesi is supplied as a ready-to-use solution, not a powder. The label says to store it at or below 25°C (77°F), not frozen, protected from light. There is no labeled storage guidance for research-grade powders.
Not applicable to Vyleesi, which comes as a single-dose autoinjector. No published stability data exist for reconstituted research-grade PT-141.
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