In the trials behind the FDA-approved bremelanotide product (Vyleesi), the most common side effects were nausea (40% vs 1.3% on placebo), flushing (20%), injection-site reactions (13%) and headache (11%). Each dose also caused a temporary blood pressure rise, up to 6 mmHg systolic, and a small drop in heart rate. Repeated daily dosing caused dark skin patches in a large share of people in one study. All of this comes from trials in premenopausal women. Vyleesi isn't indicated for men, so there's no label-grade safety table for male users.
Where the numbers come from
PT-141 is the research name for bremelanotide, a melanocortin receptor agonist. The FDA-approved version, Vyleesi, is indicated for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women. The label explicitly says it isn't indicated for postmenopausal women or for men. As labeled, it's a 1.75 mg subcutaneous autoinjector used as needed, with no more than one dose in 24 hours and no more than 8 doses a month recommended. Those are label facts for the approved product, not guidance for anyone else.
Everything below comes from that label unless noted. For how PT-141 works and how it compares with ED drugs, see our PT-141 profile and PT-141 vs Viagra vs Cialis.
The adverse reaction table
| Side effect | Vyleesi (n=627) | Placebo (n=620) |
|---|---|---|
| Nausea | 40.0% | 1.3% |
| Flushing | 20.3% | 0.3% |
| Injection-site reactions | 13.2% | 8.4% |
| Headache | 11.3% | 1.9% |
| Vomiting | 4.8% | 0.2% |
How to read these percentages
The useful number isn't the raw rate. It's the gap between drug and placebo, because that gap is what the drug added. Using the label's figures:
- Nausea: 40.0% vs 1.3%, a gap of almost 39 points. Nearly all of it is the drug.
- Flushing: 20.3% vs 0.3%, about 20 points. Again, almost entirely drug-related.
- Headache: 11.3% vs 1.9%, about 9 points.
- Injection-site reactions: 13.2% vs 8.4%, about 5 points. Much of this comes from injecting anything at all, which is why placebo users reported it too.
Two more caveats. These were trials of as-needed use, capped by the label's limits, so they say little about frequent use. And because the label contraindicates use in people with uncontrolled high blood pressure or known cardiovascular disease, these numbers don't describe what happens in those groups, which are exactly the men most likely to run into trouble with a blood pressure bump.
Nausea: the main reason people stop
Nausea is the defining side effect. It affected 40% of people on Vyleesi. Thirteen percent needed anti-nausea medication, and 8% dropped out of the trials because of it, compared with none on placebo. The label notes that for most people nausea improved by the second dose.
If you're thinking about bremelanotide for sexual activity, that matters: a drug that makes 4 in 10 users nauseated in the hours before sex has an obvious practical cost, separate from any safety question.
Flushing and headache
Flushing (20%) and headache (11%) were the next most common. They're usually short-lived, but flushing in particular is noticeable, and it isn't what most people want in an intimate setting.
Blood pressure and heart rate
This is the side effect that matters most for men, who tend to have higher cardiovascular risk at a given age. Per the label:
- Each dose causes a transient rise in blood pressure: up to 6 mmHg systolic and 3 mmHg diastolic in the trials, peaking 2 to 4 hours after dosing.
- Heart rate fell by up to 5 beats per minute.
- Values usually returned to baseline within 12 hours.
- Bremelanotide is contraindicated in people with uncontrolled high blood pressure or known cardiovascular disease, and the label advises against use in people at high cardiovascular risk.
Six mmHg isn't much in a healthy person at rest. It's a different picture for a man with borderline hypertension, on blood pressure medication, or stacking it with other things that raise blood pressure. That's exactly the gap the women-only trials leave open.
Skin darkening (focal hyperpigmentation)
Melanocortin agonists can darken skin. In the Vyleesi trials, focal hyperpigmentation, meaning localized patches of darker skin, occurred in 1% of patients using up to 8 doses a month, and in none on placebo. In a separate study where people took it for 8 consecutive days, 38% developed it. Darker skin raised the risk, and the label notes that the patches didn't resolve in every case.
That second number is the one research-peptide users should notice. Frequent use, the opposite of the label's as-needed pattern, is precisely the scenario where hyperpigmentation showed up most.
Drug interactions
The label warns that bremelanotide may significantly reduce absorption of oral naltrexone and says to avoid combining it with oral naltrexone products used for alcohol or opioid dependence. If you take any regular medication, especially for blood pressure, ask a prescriber before using it.
The evidence gap for men, stated plainly
Known (label): side-effect rates, blood pressure effect and pigmentation risk in premenopausal women using an approved autoinjector as needed. Not established: side-effect rates in men, effects in men with hypertension or heart disease, interactions with ED medications, and the safety of frequent or long-term use. Different product altogether: research-grade "PT-141" vials, which aren't sold for human use and have no approved human dose.
Some telehealth services prescribe compounded bremelanotide to men off-label. Compounded versions aren't FDA-approved, and their side-effect profile hasn't been studied separately from Vyleesi. A prescriber choosing that route should screen your blood pressure and cardiovascular history first. Our PT-141 for men overview covers what's known about the male-specific research.
Before you consider PT-141: a short checklist
- Know your blood pressure: a recent, accurate reading, not one from years ago.
- List every medication, including oral naltrexone and blood pressure drugs.
- Be clear about the problem. Low desire, erectile function and low testosterone are different problems with different treatments. If desire has dropped along with energy, get testosterone checked; our TRT vs peptide clinic guide covers the workup.
- Ask whether the prescription is an approved product or compounded, and which pharmacy fills it. Our clinic checklist has the full list of questions.
- Ask what to do about nausea before you need to.
Prescription options we link to
Both services put the decision with a licensed clinician, who may recommend an approved ED or libido treatment instead:
Dosing for prescription products is set by the prescribing clinician. Research-use-only peptides are not sold for human use and have no approved human dose. See our medical disclaimer and the sexual performance hub.
Chest pain, a severe headache, fainting, or vomiting you can't stop after any sexual-health drug needs urgent care. Tell the treating clinician what you took.
Sources
- FDA, Vyleesi (bremelanotide injection) prescribing information (2019): indication and limitations of use, dosing limits, contraindications, blood pressure and heart rate, focal hyperpigmentation, nausea, adverse reaction table, naltrexone interaction.
Frequently Asked
In the trials behind the approved product Vyleesi, the most common were nausea (40 percent vs 1.3 percent on placebo), flushing (about 20 percent), injection-site reactions (about 13 percent) and headache (about 11 percent).
Yes, temporarily. The Vyleesi label reports increases of up to 6 mmHg systolic and 3 mmHg diastolic, peaking 2 to 4 hours after a dose, with heart rate dropping by up to 5 beats per minute. Values usually returned to baseline within 12 hours. It is contraindicated in uncontrolled hypertension and known cardiovascular disease.
No. Vyleesi is approved for hypoactive sexual desire disorder in premenopausal women, and its label states it is not indicated for men. There is no label-grade safety data for men.
It can. Focal hyperpigmentation occurred in 1 percent of trial patients using up to 8 doses a month, but in 38 percent of people in a study of 8 consecutive daily doses. Darker skin raised the risk, and not every case resolved.
The label does not give a duration, but it reports that nausea improved for most patients by the second dose. In the trials, 13 percent needed anti-nausea medication and 8 percent stopped because of nausea.