What is PT-141?

What sources report

What PT-141 is

PT-141 was the development code Palatin Technologies used for bremelanotide, which it made as an analog of melanotan II (MT-II).⁸ The FDA label describes bremelanotide acetate as a synthetic cyclic heptapeptide: seven amino acids, part of them closed into a ring, with the sequence Ac-Nle-cyclo-(Asp-His-D-Phe-Arg-Trp-Lys-OH).¹ PubChem lists the free base as C50H68N14O10, with a molar mass of 1025.2 g/mol, under CID 9941379.⁹ Its CAS number is 189691-06-3.⁵ In the approved drug, 1.75 mg of bremelanotide equals 1.89 mg of the acetate salt.¹

How it acts

Bremelanotide activates several melanocortin receptors without selectivity.¹ In order of potency, these are MC1R, MC4R, MC3R, MC5R and MC2R.¹ The label states that the mechanism by which Vyleesi improves HSDD in women is unknown.¹ MedlinePlus describes it as activating natural substances in the brain that control mood and thinking.¹⁴ A 2022 review proposes that it acts on MC4 receptors in the medial preoptic area of the hypothalamus, raising dopamine release, a model that rests mainly on animal studies.⁷ In 2003, researchers reported that it caused penile erections when given to rats and nonhuman primates.⁴ After an injection under the skin, bioavailability is about 100%, blood levels peak at a median of about 1 hour, and the half-life is about 2.7 hours (label).¹

Research timeline

• 2003: a paper describes PT-141 as an alpha-MSH analog that acts at melanocortin receptors.⁴
• 2004 and 2005: small studies in men test injected and nasal doses, alone and with sildenafil.¹⁵¹⁶¹⁷
• 2008: a trial in 342 men is published; in 2023 the journal attaches an expression of concern to it.¹⁸
• 2016: a 12-week dose-finding trial in premenopausal women compares three doses with placebo.¹⁹
• 2019: the phase 3 results are published and FDA approves Vyleesi.²⁰²
• 2022: a review of the development program, about 3,500 people in 43 studies, reports no deaths and few serious adverse events.²¹
• 2026: FDA warning letters name PT-141 sold online, FDA approves a label update after the breastfeeding trial, and a journal viewpoint asks whether bremelanotide should be considered for men.¹³²²²³

Evidence in people

The strongest evidence comes from two identical 24-week phase 3 trials, called RECONNECT, in 1,267 premenopausal women with acquired, generalized HSDD.²⁰ Women used 1.75 mg by autoinjector as needed.¹ Compared with placebo, desire scores rose 0.30 and 0.42 points more, and distress about low desire fell 0.37 and 0.29 points more.²⁰ The number of satisfying sexual events did not differ significantly from placebo.¹ Independent re-analyses published in 2021 and 2024 judged the effects small to nil.²⁴²⁵ The trial investigators published a commentary disputing the 2021 re-analysis.²⁶

Evidence in men comes from small studies, mostly of a nasal form, and from a 2008 trial that now carries an expression of concern.¹⁵¹⁶¹⁸ FDA has not approved any use in men.¹ Full list: PT-141 benefits and uses. The goal pages cover PT-141 and women's health and PT-141 and men's health.

How it compares

• Vyleesi: the same molecule, as the FDA-approved 1.75 mg/0.3 mL prescription autoinjector.¹² See What is Vyleesi?.
• Melanotan II: the parent compound. PubChem lists it as C50H69N15O9 (1024.2 g/mol), ending in an amide rather than a free acid.¹⁰⁹ FDA's compounding safety page lists melanotan II among substances nominated and later withdrawn, and a 2026 review notes it is still found in unregulated markets.¹²²⁷ See What is Melanotan 2?.
• Sildenafil (Viagra): a PDE5 inhibitor for erectile dysfunction.¹⁵ It increases blood flow to the penis during sexual stimulation and does not increase desire.²⁸
• Flibanserin (Addyi): a pill taken once daily at bedtime for certain women with HSDD, acting on serotonin receptors.²⁹ Alcohol near a dose raises the risk of very low blood pressure.²⁹

Side effects

In the phase 3 trials, nausea affected 40% of women on bremelanotide versus 1.3% on placebo.¹ Flushing (20.3%), injection site reactions (13.2%) and headache (11.3%) came next.¹ Each dose briefly raises blood pressure, by up to 6 mmHg systolic, and lowers heart rate by up to 5 beats per minute.¹ Darker patches of skin appeared in 1% of women using up to 8 doses a month and in 38% given daily doses for 8 days.¹ Full list: PT-141 side effects.

Dosage information

The only established human dose is the Vyleesi label dose for premenopausal women with HSDD, and the prescriber sets the dose for each patient.¹ It is 1.75 mg under the skin of the abdomen or thigh, as needed, at least 45 minutes before anticipated sexual activity, and no more than once in 24 hours.¹ The label advises against more than 8 doses a month and says to stop after 8 weeks without improvement.¹ No dose is approved for men or postmenopausal women, and research vials have no FDA-reviewed directions.¹³ Full details: PT-141 dosage.

Reconstitution and storage

Vyleesi needs no mixing. It is a clear 1.75 mg/0.3 mL solution in a single-dose autoinjector, with 2.5% glycerin and sterile water for injection among its inactive ingredients.¹ Its label calls for storage at or below 25°C (77°F), no freezing and protection from light.¹

Research PT-141 is a different product. The 10 mg research vial sold here holds a white freeze-dried solid, and bacteriostatic water is a separate item. No FDA-reviewed reconstitution or storage directions exist for such vials.³ General lab steps are in How to reconstitute a peptide vial and How to store peptides. The reconstitution calculator works out concentration from vial mass and diluent volume. The research vial is listed as PT-141 for sale, labeled for research use.

Regulatory status

FDA approved bremelanotide as Vyleesi (NDA 210557) on June 21, 2019, as a new molecular entity.² The approval letter went to AMAG Pharmaceuticals.⁶ As of October 2026, Drugs@FDA lists Cosette as the application holder, and the label says Cosette Pharmaceuticals markets the drug.²¹ The approved use is acquired, generalized HSDD in premenopausal women.⁶ The label excludes men, postmenopausal women and use to enhance sexual performance.¹

At approval, FDA required a trial in breastfeeding women and two pregnancy outcome studies; the pregnancy studies are scheduled to finish in May 2030.⁶ On October 23, 2026, FDA approved a labeling supplement (S-005) that updates the label section on specific populations, based on the breastfeeding trial.²²² As of October 24, 2026, the updated text was not posted on Drugs@FDA.²

No approved application covers PT-141 sold for research.³ On August 24, 2026, FDA warning letters to TXP Innovations (Tex Peptides) and NuScience Peptides named PT-141 among unapproved new drugs under section 505(a) of the FD&C Act.¹³³ FDA said research-use labeling, such as "research use only", did not change its conclusion, because the sellers' websites showed the products were intended for human use.¹³³ The same letters treated bacteriostatic water sold for reconstituting peptides as a drug.³¹³ Our sources did not confirm the status of bremelanotide on the WADA Prohibited List or any approval outside the United States.