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Strong human trialsFDA approved as Vyleesi

PT-141 side effects

Also known as: Bremelanotide · Vyleesi · PT141

Updated 29 sources

18 side effects reported for PT-141: 15 from studies and labels, 3 from users and guides. 4 come with the ways people manage them.

PT-141 overview

Side effects reported in studies and labels

Rates as each trial or label states them. A rate from one trial does not carry over to research-grade vials or other doses.

From trials and regulators15

Clinical studies and regulatory documents.

  • Nausea

    40.0% vs 1.3% on placebo in phase 3. Starts within about 1 hour, lasts about 2. Hit 21% after the first dose, about 3% later; 8% quit over it.

    How people manage it

    • The label allows an anti-nausea drug; 13% of trial users took one.

  • Flushing

    20.3% on bremelanotide vs 0.3% on placebo in phase 3 (1.75 mg).

  • Injection-site reactions

    13.2% on bremelanotide vs 8.4% on placebo in phase 3 (1.75 mg).

  • Headache

    11.3% on bremelanotide vs 1.9% on placebo in phase 3 (1.75 mg).

  • Vomiting

    4.8% on bremelanotide vs 0.2% on placebo in phase 3 (1.75 mg).

  • Cough

    3.3% on bremelanotide vs 1.3% on placebo in phase 3 (1.75 mg).

  • Fatigue

    3.2% on bremelanotide vs 0.5% on placebo in phase 3 (1.75 mg).

  • Hot flush

    2.7% on bremelanotide vs 0.2% on placebo in phase 3 (1.75 mg).

  • Tingling or numbness (paraesthesia)

    2.6% on bremelanotide vs 0.0% on placebo in phase 3 (1.75 mg).

  • Dizziness

    2.2% on bremelanotide vs 0.5% on placebo in phase 3 (1.75 mg).

  • Nasal congestion

    2.1% on bremelanotide vs 0.5% on placebo in phase 3 (1.75 mg).

  • Temporary rise in blood pressure

    Peak rise of 6 mmHg systolic and 3 diastolic at 2 to 4 hours, heart rate down up to 5 bpm. Back to baseline within about 12 hours; no build-up with daily doses.

    How people manage it

    • Avoid it with uncontrolled high blood pressure or known heart disease, per the label.

  • Dark skin patches (face, gums, breasts)

    1% at up to 8 doses a month; 38% after 8 daily doses in a row, plus 14% more after 8 more days. More likely with darker skin; not always reversible.

    How people manage it

    • Keep doses infrequent. The label caps use at 8 a month, and the risk climbs with daily dosing.

  • Acute hepatitis

    One case in the open-label extension; a link to the drug could not be ruled out.

  • Flushing and nausea in men (nasal trials)

    The most common side effects in the men's intranasal trials. No rates given in the abstract.

Side effects users and guides report

What people post and what dosing guides list. These are reports, not measured rates.

From users and guides3

Community reports, competitor and vendor guides, media.

  • Lower appetite

    A mild appetite drop, reported in one r/Peptides comment.

  • Nausea, headache and injection-site irritation (community logs)

    The most logged side effects in one site's user logs. On r/Peptides, headache and nausea are the main complaints, and some users quit over them. Users also describe hot eyes.

    How people manage it

    • Start very low and work up, the standard r/Peptides advice after a bad first dose.

  • Dark spots at low, frequent doses (community report)

    One r/Peptides user reported new moles, dark spots and darker under-eye circles after under 1 mg every other day for 4 days.

Who should avoid it, and what not to combine

  • Uncontrolled high blood pressure or known cardiovascular diseaseCondition

    PT-141 raises blood pressure for a few hours after each dose. The label says not to use it with uncontrolled hypertension or known heart disease.

  • Oral naltrexoneSubstance

    Bremelanotide can sharply cut naltrexone levels in the blood, which can make naltrexone fail, per the label.

  • Melanotan IISubstance

    Both hit the same melanocortin receptors. Guides warn against stacking two melanocortin agonists.

How much is known

Strong human trials

About 3,500 people across 43 studies. Two phase 3 trials in 1,267 women showed small but real gains in desire and less distress; about 25% vs 17% on placebo improved meaningfully, but satisfying sexual events did not rise. 18% quit over side effects vs 2% on placebo. Male data is limited to phase 1/2 trials, and the main non-responder trial has an expression of concern.

PT-141 side effects questions

Why does PT-141 cause nausea, and how do I stop it?

Nausea hit 40% of women in the phase 3 trials, usually within an hour and lasting about 2 hours. It was worst after the first dose (21%) and dropped to about 3% on later doses. The label allows an anti-nausea drug, and 13% used one. Guides suggest starting at 0.5 to 1 mg, taking ondansetron 30 minutes before, eating a light meal 1 to 2 hours before, and staying hydrated.

Is PT-141 safe with high blood pressure?

The label says not to use it with uncontrolled high blood pressure or known heart disease. Each dose raises blood pressure by about 6/3 mmHg at its peak, 2 to 4 hours after the shot, and lowers heart rate by up to 5 beats a minute. Both usually return to baseline within 12 hours.

Sources for these side effects

12 sources, each checked by date. Record updated Oct 23, 2026. Numbers are restated in our own words and labelled by where they came from.

Regulatory2

  1. Vyleesi (bremelanotide) prescribing information, 2019FDA · checked Oct 23, 2026
  2. Vyleesi label (current)DailyMed · checked Oct 23, 2026

Competitor guide3

  1. Bremelanotide (PT-141) protocolpeptidedosingprotocols.com · checked Oct 23, 2026
  2. PT-141peptidesexplorer.com · checked Oct 23, 2026
  3. PT-141peptidedeck.com · checked Oct 23, 2026

Community-reported6

  1. Comment: appetite effectr/Peptides · checked Oct 23, 2026
  2. PT-141peptiq.io, via a competitor guide · checked Oct 23, 2026
  3. Comment: headache and nausea, start lowr/Peptides · checked Oct 23, 2026
  4. Comment: worst day, never againr/Peptides · checked Oct 23, 2026

Back to the full PT-141 page for dosing, the vial chart and storage.