PT-141
Melanocortin receptor agonist · Bremelanotide. Marketed as Vyleesi in the United States
- UK status
- Not licensed in the UK
- Availability
- Licensed in the US only
- Evidence base
- Human RCT for its licensed indication
- Controlled drug
- No
Sequence
A synthetic cyclic heptapeptide, an analogue of alpha-MSH.
The short version
What it does
Increases sexual desire. In the US it is a licensed medicine for one specific diagnosis in one specific group of women, taken before sex rather than daily.
How it does it
Acts on switches in the brain that influence sexual motivation, rather than on blood flow the way Viagra does. That is a real difference: it works on wanting, not on plumbing.
The catch
It is licensed for premenopausal women with a diagnosed desire disorder. It is sold online to men, to older women, and for recreational use, none of which it was approved for or trialled in.
Everything below goes into the detail, with sources.
PT-141 came out of the same research that produced melanotan. Somebody noticed that a tanning peptide had an unexpected side effect, and followed it. That is the origin story of a licensed medicine, and also of a great deal of grey-market selling.
At a glance
- Compound type
- Cyclic heptapeptide, an alpha-MSH analogue
- Generic name
- Bremelanotide
- Drug class
- Melanocortin receptor agonist
- Route
- Injection, autoinjector, used on demand
- US approval
- 2019, as Vyleesi
- Licensed indication
- Hypoactive sexual desire disorder in premenopausal women only
- UK status
- No MHRA authorisation
- Main safety consideration
- Transient rises in blood pressure. The nasal version was abandoned over this.
- Related compound
- Melanotan II, from the same line of research
01What it is
Alpha-MSH, the hormone melanotan copies, acts on a family of melanocortin receptors that do several unrelated jobs: pigmentation, appetite, inflammation and sexual function among them. PT-141, generic name bremelanotide, is a synthetic cyclic peptide engineered to hit the receptor subtypes involved in sexual motivation while avoiding the pigmentation effects.
It acts centrally, in the brain, which distinguishes it from sildenafil and the rest of that class. Those work on blood flow, so they help with the mechanics of arousal. This is aimed at desire itself.
02How it came about
The compound emerged from work on melanotan peptides, originally investigated for skin tanning. Researchers noticed effects on sexual arousal, and development followed that thread.
Bremelanotide was initially developed as a nasal spray, which was abandoned after blood pressure increases were observed. Reformulated as an injection, it was tested in the phase 3 RECONNECT programme, two trials with roughly 1,247 premenopausal women with hypoactive sexual desire disorder, and the FDA approved it in 2019 as Vyleesi.
It is now also being studied for an unrelated purpose: a phase 2 trial is testing bremelanotide alongside tirzepatide for obesity, on the basis that melanocortin receptors are also involved in appetite regulation.
03UK legal and licensing status
PT-141 is FDA-approved in the United States as Vyleesi, for acquired, generalised hypoactive sexual desire disorder in premenopausal women. That is the whole licensed indication.
Bremelanotide has no MHRA marketing authorisation. It is not a licensed medicine in the UK and cannot lawfully be supplied for human use here.
Premenopausal women. Diagnosed HSDD, meaning distressing low desire that is acquired and not explained by another cause. That is who the trials studied and who the licence covers.
It is sold online to men for erectile function and libido, to postmenopausal women, and recreationally. None of those populations were in the pivotal trials. The nasal formulation was abandoned over blood pressure, and blood pressure effects do not become irrelevant because a different group is using it.
04How it works
It activates melanocortin receptors in the central nervous system, principally MC4R, influencing the neural circuits involved in sexual motivation. It is used on demand, before anticipated activity, rather than continuously.
Because melanocortin receptors also regulate appetite and blood pressure, effects on both are expected rather than surprising, which is where the phase 2 obesity work comes from and also where the cardiovascular caution comes from.
05What it is not
Claims that attach themselves to this compound and do not hold up.
- Not a Viagra equivalent. Different mechanism entirely. Sildenafil affects blood flow; this affects desire. They are not substitutes and are not interchangeable.
- Not licensed for men. The approval covers premenopausal women with a specific diagnosis. Trials in men did not produce an approval.
- Not licensed in the UK at all. A US approval does not transfer.
- Not free of cardiovascular caution. The nasal version was abandoned over blood pressure increases. That history matters.
06What the evidence shows
The RECONNECT trials are real phase 3 evidence: randomised, placebo-controlled, around 1,247 premenopausal women with diagnosed HSDD, and they supported an FDA approval.
The effect sizes in HSDD trials are modest and the outcome measures are questionnaire-based, which is unavoidable when measuring desire but does limit precision. More importantly for anyone reading this in the UK: none of that evidence covers men, postmenopausal women, or people without the diagnosis.
The phase 2 obesity work with tirzepatide is early and unrelated to the licensed use. It should not be read as evidence for anything yet.
Any evidence in men or postmenopausal women. Long-term safety, since the licensed use is on-demand rather than continuous. And no UK regulatory assessment at all, so no SPC and no Yellow Card coverage.
07Reported harms
For its licensed use, the US prescribing information carries the full frequency table. Nausea is common and can be significant. Injection site reactions, flushing and headache are reported. Transient increases in blood pressure with decreases in heart rate are recognised, which is why it is not recommended in people with uncontrolled hypertension or known cardiovascular disease.
Darkening of the skin or gums can occur, which is unsurprising given the parent hormone, and may not fully resolve.
Unlicensed product bought online carries the usual identity, purity and sterility problems, and falls outside Yellow Card.
08Interactions and cautions
The blood pressure effects are the practical concern, particularly alongside antihypertensives or anything else affecting blood pressure. Because the licensed product is on-demand, interactions with alcohol and recreational drugs are a real-world question the trials did not systematically address.
09Stopping
Not applicable in the usual sense, since licensed use is on demand rather than continuous. There is no described withdrawal effect.
10Monitoring
In licensed US use, blood pressure is the thing a prescriber would care about before and during treatment. Bought online for a use it was never approved for, nobody is checking anyone's blood pressure.
11Questions worth asking
Take these to a doctor or pharmacist. A good clinician will not mind being asked, and the answers are specific to you in a way nothing on this page can be.
- Am I in the group this was actually licensed and trialled for?
- Do I know what my blood pressure is, given this raises it?
- Is there something treatable behind low desire, such as a medication, a thyroid problem or depression, that nobody has looked for?
12Common questions
Is PT-141 legal in the UK?
It has no MHRA authorisation, so supplying it for human use here is prohibited. It is a licensed medicine in the United States, marketed as Vyleesi, but a US approval does not transfer to the UK.
Does PT-141 work for men?
Not established. The approval and the pivotal phase 3 trials covered premenopausal women with a diagnosed desire disorder. Trials in men did not lead to an approval, and the marketing aimed at men is not based on an approved indication.
How is it different from Viagra?
Sildenafil works on blood flow, helping the physical mechanics of arousal. PT-141 acts on brain circuits involved in sexual motivation. They address different problems and are not substitutes.
Why was the nasal spray version abandoned?
Because increases in blood pressure were observed during development. It was reformulated as an injection. That history is the reason blood pressure is the main safety consideration for the approved product.
13Sources
Links go to the authoritative source. Where a document sits behind a paywall or moves around, the full citation is given so you can find it yourself.
- US prescribing information for VyleesiFDA
- RECONNECT phase 3 trialsPubMed
- Bremelanotide with tirzepatide, phase 2 NCT06565611ClinicalTrials.gov
- Melanotan II record/compounds/melanotan-ii/
- Unlicensed medicines guidanceMHRA
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