Page last checked 2026-08-12

Melanocortin receptor agonist · safety

PT-141 side effects

Also written PT 141 or PT141.

The pt-141 side effects reported most often are nausea, flushing and injection site reactions. The full list is below, with the FDA label cited at the bottom of the page.

Rarer, but worth being able to spot: transient rise in blood pressure with a fall in heart rate, focal hyperpigmentation and severe or persistent nausea.

The sources describe these effects in relation to the dose and to the early weeks.

PT-141 is the development code for bremelanotide. It acts on melanocortin receptors in the brain, rather than on blood flow the way the erectile-dysfunction pills do. It is bought mostly by men, for erections and desire.

That is the one group its label rules out. Vyleesi was approved in 2019 for premenopausal women with low sexual desire. The same label excludes postmenopausal women, and use to improve sexual performance. In the trials behind it, 18% of participants stopped because of a reaction.

Also sold as Vyleesi — one molecule, so these reactions apply to every brand of it.

Further down: the full list with frequencies · when to get medical help · questions

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-08-12open the primary sources

At a glance

Common reactions listed

Serious reactions listed

Boxed warning

None on label

Strongest source

FDA label

The counts show how many distinct reactions the FDA label names. The percentages show how often a reaction appeared in a study group, not the chance that it will happen to you.

Common reactions

The full list, with the frequency band the FDA label gives for each one.

◆ Common reactionslabel frequency

Reaction	Frequency
Nausea	40.0% vs 1.3% on placebo
Flushing	20.3% vs 0.3% on placebo
Injection site reactions	13.2% vs 8.4% on placebo
Headache	11.3% vs 1.9% on placebo
Vomiting	4.8% vs 0.2% on placebo
Cough	3.3% vs 1.3% on placebo
Fatigue	3.2% vs 0.5% on placebo
Hot flush	2.7% vs 0.2% on placebo
Paraesthesia	2.6% vs 0.0% on placebo
Dizziness	2.2% vs 0.5% on placebo
Nasal congestion	2.1% vs 0.5% on placebo

Serious reactions to watch for

These are rarer, and they are the ones clinicians monitor for. Seek medical care if you have symptoms.

◆ Serious — monitorwarning/precaution

Reaction	Frequency
Transient rise in blood pressure with a fall in heart rate	Labeled warning — peaks 2 to 4 hours post-dose, usually back to baseline within 12 hours
Focal hyperpigmentation (face, gums, breasts)	1% at up to 8 doses a month vs none on placebo; 38% after 8 consecutive daily doses
Severe or persistent nausea	Anti-emetic therapy needed by 13% and 8% stopped treatment because of it

FDA labelEvery reaction above comes from the product’s regulatory document. These are label facts, not personal advice.

When to seek medical care

Each one below is a serious reaction from the table above, written as the signs you would actually notice. Spotting them is the job of this section; working out what they mean is a clinician’s.

Increased heart rate

Urgent

Signs: A resting pulse that stays faster than usual, palpitations, getting out of breath doing ordinary things, or feeling lightheaded.

Report a lasting change to a clinician, who can put it next to the rest of the picture. Chest pain, fainting, or breathlessness while resting is an emergency call, not a clinic call.

EmergencySome symptoms should not wait for an appointment. Call emergency services (911 in the US) if they are severe, getting worse fast, or involve trouble breathing, chest pain, fainting or confusion.

2Read deeperTiming, evidence limits, and product context

When these effects tend to occur

The cited evidence describes these effects in relation to the dose and to the early period of taking it, rather than as a constant background throughout.

When a study reports how side effects changed over time, it describes the group as a whole. It cannot predict one person’s experience.

Vyleesi side effects

Vyleesi is a brand name for pt-141. The frequency bands above describe the molecule. Percentages can still differ by brand because each label may be based on different trials, doses and groups of people.

FDA has approved this molecule, but only as Vyleesi.

Vyleesi is a prescription autoinjector holding a ready-made solution. Its label has no powder vial and no reconstitution step anywhere in it. Research-grade PT-141 sold as a lyophilized powder is not that product, and no approved label stands behind it.

The label caps use at one dose in 24 hours. It advises against more than 8 doses a month. It rules the drug out entirely in uncontrolled hypertension or known cardiovascular disease.

Common questions

How long do pt-141 side effects last, and do they go away?

The sources do not commit to a set number of days. What they describe is a pattern — reactions cluster after you start and after each increase, then ease while the dose is held steady. Any page quoting an exact number of days is quoting something the sources do not say.

What are the most common pt-141 side effects?

Nausea, flushing, injection site reactions and headache — the table above has the rest, each with its frequency band and source.

Does pt-141 have a boxed warning?

No — its label carries none. That reflects what regulatory review has and has not covered, not a finding that serious risks were looked for and ruled out.

Can the pt-141 dose be lowered if side effects are hard to tolerate?

That decision belongs to the prescribing clinician. The label sets a single dose rather than a ladder, so there is no step to hold at. Any change to it sits with the prescriber.

Does pt-141 cause hair loss?

Hair loss is not among the reactions listed on this page for pt-141, because the FDA label cited here does not carry it. Anything missing from the tables is outside what can be sourced here rather than ruled out, and a symptom that worries you belongs with a clinician.

Is fatigue a listed pt-141 side effect?

Yes — it is in the common reactions table above, with its frequency band. Being listed means it came up often enough in the trial population to reach the FDA label; it does not establish the cause in any one case.

Is constipation a listed pt-141 side effect?

Not separately. If a source groups stomach and gut events together, this page keeps that group intact. It does not invent named reactions the source never listed.

What should someone do about a serious pt-141 reaction?

Contact a clinician promptly, and emergency services if symptoms are severe or getting worse quickly. The section above describes what those reactions actually look like, so they can be spotted early rather than explained away.

Do the frequencies on this page mean the chance it happens to one person?

No. These figures describe groups in a study. A band shows how often a reaction appeared under that trial’s conditions. It cannot predict what will happen to one person.

The schedule these reactions were recorded against, the comparisons, and the sourcing rules behind every grade on this page.

The molecule behind Vyleesi

No published half-life figure was found for PT-141.

Work out the PT-141 draw in syringe units

Vial sizes 1.75 mg for PT-141, each with its own concentration.

The PT-141 page on taking two at once

Nothing on it is built by inference — no mechanism, no “probably avoid”, no assembled list, with PT-141 as context

Every calculator on this site, PT-141 and the rest

Every intermediate value is printed, for PT-141 or any other vial.

Fatigue across every page, not just PT-141

5 of 36 pages carry fatigue, counted class-wide rather than within PT-141.

Nausea across every page, not just PT-141

12 of 36 pages carry nausea, counted class-wide rather than within PT-141.

Primary regulatory documents, including PT-141

Every URL was fetched and live on its retrieval date, PT-141 or otherwise.

Where PT-141 sits among the source-checked pages

See the strongest source available for every compound, with PT-141 as context

Questions readers ask

Is PT-141 better than Viagra?

No trial has compared them, so on side effects there is nothing to weigh one against the other. What PT-141 has is a full label table from two 24-week trials, covering 627 treated participants and 620 on placebo.

That table is not a gentle one. Eighteen percent of participants left the trials because of a reaction, and serious reactions turned up in 1.1 percent.

How long does the effect of PT-141 last?

The label publishes no duration of effect. What it does time is the blood-pressure rise, which peaks two to four hours after a dose and usually settles back within twelve. The label also gives a mean half-life of about 2.7 hours.

Use is capped at one dose in twenty-four hours, with more than eight doses a month advised against. Those are label limits, not a measure of how long anything lasts.

What are the risks of using PT-141?

The label rules the drug out entirely in uncontrolled high blood pressure and known heart or blood-vessel disease. Its warning covers a short rise in blood pressure with a fall in heart rate after each dose.

Darkening of skin on the face, gums or breasts showed up in 1 percent at up to eight doses a month. After eight days running it reached 38 percent. Severe or lasting nausea needed anti-sickness treatment in 13 percent, and 8 percent stopped because of it.

What does PT-141 make you feel like?

Nausea is the most common thing on the label table: 40 percent of treated participants against 1.3 percent on placebo. Flushing followed at 20.3 percent, then headache at 11.3 and vomiting at 4.8.

Further down sit fatigue, hot flushes, dizziness, tingling, cough and a blocked nose, each in two to three percent of participants. These are group figures from two trials, not a forecast for one person.

1primary source, each with the day we read it — open the documents used on this page

VYLEESI (bremelanotide) injection — FDA-approved Prescribing Information (DailyMed SPL)retrieved 2026-08-12FDA label