What is bremelanotide?

Bremelanotide is a seven-amino-acid cyclic peptide and a close relative of melanotan II: it is what melanotan II becomes when the body converts one end group, and it was pursued after the tanning peptide's unexpected effect on erections was noticed in the 1990s. Like its parent, it binds several melanocortin receptors, and its sexual effect is thought to run through the MC4 receptor in the brain rather than through blood flow in the genitals, which is the difference from sildenafil. It was developed under the code name PT-141 and, as Vyleesi, was approved by the U.S. FDA in 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder — low desire that causes distress and is not explained by another condition, a relationship problem or a medicine. The approved form is an injection under the skin from a single-use autoinjector. Everything in this guide about effect size and side effects comes from the trials behind that approval.

PT-141What the studies show

Q: What kind of evidence exists for bremelanotide?

Large human trials. Two large placebo-controlled trials in premenopausal women behind an FDA approval, showing a small effect on desire and a high rate of nausea; small early trials in men; no long-term data.

A metabolite of a tanning peptide that became Vyleesi, the first as-needed drug approved for low sexual desire in premenopausal women.

5 min read · Large human trials · Updated November 2026

In short

Name: bremelanotide (sold by Progression Labs as PT-141)
Evidence: Large human trials
Bottom line: Two large placebo-controlled trials in premenopausal women behind an FDA approval, showing a small effect on desire and a high rate of nausea; small early trials in men; no long-term data.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Bremelanotide is a seven-amino-acid cyclic peptide and a close relative of melanotan II: it is what melanotan II becomes when the body converts one end group, and it was pursued after the tanning peptide's unexpected effect on erections was noticed in the 1990s ¹. Like its parent, it binds several melanocortin receptors, and its sexual effect is thought to run through the MC4 receptor in the brain rather than through blood flow in the genitals, which is the difference from sildenafil ¹. It was developed under the code name PT-141 and, as Vyleesi, was approved by the U.S. FDA in 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder — low desire that causes distress and is not explained by another condition, a relationship problem or a medicine ². The approved form is an injection under the skin from a single-use autoinjector ². Everything in this guide about effect size and side effects comes from the trials behind that approval.

The studies below call this molecule bremelanotide. Progression Labs sells it as PT-141; the guide uses the store's name and the papers use theirs.

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Rats and a side effect

In 2004, researchers at Concordia University gave bremelanotide to female rats and counted one behaviour in particular: solicitations, the hops and darts a female rat uses to invite a male. Solicitations went up with the peptide while the mechanical parts of mating did not change, which pointed to an effect on motivation rather than on the body ³. That is the result the later human work set out to test.

Men first

Early development was in men. A 2004 study gave a nasal spray of PT-141 or placebo to healthy men and to men with mild-to-moderate erectile dysfunction and measured erections with a RigiScan device; the peptide produced erectile responses in both groups, in the healthy men without any visual sexual stimulation ⁴. The nasal spray was later dropped because it raised blood pressure, and the programme turned to women and to an injection ⁵.

The RECONNECT trials

The approval rests on two identical phase 3 trials, published together in 2019, that enrolled roughly 1,250 premenopausal women with the disorder and randomised them to bremelanotide 1.75 milligrams or placebo, injected under the skin as needed for 24 weeks ⁵. The two primary measures were the desire domain of a standard questionnaire, scored from 1.2 to 6, and a single question about distress. Desire rose in both groups — placebo effects in this field are large — and rose more with bremelanotide, by about 0.3 to 0.4 of a point over placebo; distress fell more as well. Both differences were statistically significant in both trials, and both are small in absolute terms; the authors reported that a larger share of women on the drug had an improvement they themselves rated as meaningful ⁵.

Nausea was the dominant side effect: about 40 percent of women on bremelanotide had it, against 1 percent on placebo, and 18 percent stopped because of side effects, against 2 percent on placebo ².

Side effects and what is not known

The label also records flushing in 20 percent, injection-site reactions in 13 percent and headache in 11 percent; a transient rise in blood pressure of about 6 mmHg systolic that peaks in the hours after each dose and settles within about 12 hours, which is why the drug is not for women with uncontrolled hypertension or cardiovascular disease; and darkening of the skin on the face, gums or breasts in 1 percent of women, more often in those with darker skin and far more often in a study where it was given daily for eight days ².

Bremelanotide has not been studied in men beyond the early trials, in postmenopausal women, or for longer than about a year. The melanocortin system it acts on also governs appetite and pigment, which is the part of its pharmacology the trials were not designed to watch.

What these studies are, and aren't

Large human trials. Two large placebo-controlled trials in premenopausal women behind an FDA approval, showing a small effect on desire and a high rate of nausea; small early trials in men; no long-term data.