PT-141

PT-141 is a seven-amino-acid cyclic peptide, Ac-Nle-cyclo-(Asp-His-D-Phe-Arg-Trp-Lys-OH), and an analogue of alpha-melanocyte-stimulating hormone (alpha-MSH) ^[12]. It was developed by Palatin Technologies as a derivative of melanotan II, a tanning and erection-inducing peptide made at the University of Arizona ^[2][11]. The two molecules differ by a single terminal group, but bremelanotide went through a full drug development programme and melanotan II did not.

Bremelanotide was first tested for erectile dysfunction in men, then redirected to low sexual desire in women. It was approved by the US Food and Drug Administration (FDA) in June 2019 under the brand name Vyleesi, supplied as a 1.75 mg autoinjector for premenopausal women with acquired, generalised hypoactive sexual desire disorder, meaning low desire that causes marked distress and is not due to another medical or psychiatric condition, relationship problems or medication ^[11][12].

“PT-141” is the name most often used by research peptide vendors, whose products are not the licensed medicine and are sold as powders for reconstitution rather than as the approved autoinjector.

Bremelanotide activates several melanocortin receptors; the Vyleesi label lists the order of potency as MC1R, MC4R, MC3R, MC5R and MC2R ^[12]. The effect on sexual desire is thought to involve MC4 receptors in the brain, particularly the hypothalamus, rather than a direct effect on blood flow. The label states that the mechanism by which it improves desire in women is not known ^[12].

Early developers showed that PT-141 given to rats activated neurons in the hypothalamus and produced erections in rats and non-human primates ^[1]. In female rats, bremelanotide selectively increased “solicitation”, a measure of sexual appetite, without changing receptive behaviour, and the effect was reproduced by infusion into the medial preoptic area of the brain ^[13]. This central mode of action is different from sildenafil-type drugs, which act on blood vessels in the penis.

Activation of MC1 receptors on skin pigment cells explains why darkening of the skin (focal hyperpigmentation) can occur, especially with frequent dosing, and MC4 activation is linked to the small transient rises in blood pressure seen in trials ^[8][9].

In early placebo-controlled studies, intranasal PT-141 produced dose-dependent erections in healthy men and in men with mild-to-moderate erectile dysfunction who responded to sildenafil. Erections were statistically significant compared with placebo at doses above 7 mg, with onset around 30 minutes; flushing and nausea were the most common side effects ^[3].

A 2008 Iranian trial randomised 342 men who had not responded to sildenafil to intranasal bremelanotide 10 mg or placebo and reported a better response with bremelanotide (33.5% versus 8.5%) ^[4]. The journal published an expression of concern about this paper in 2023, so its findings should be treated with caution. Development for erectile dysfunction was later dropped in favour of the women’s indication, and Vyleesi is not approved for use in men ^[12].

A phase 2b dose-finding study in premenopausal women with HSDD and/or female sexual arousal disorder found that the 1.75 mg subcutaneous dose produced statistically significant responder rates compared with placebo across seven patient-reported endpoints ^[5]. That dose was taken into phase 3.

The phase 3 RECONNECT programme consisted of two identical randomised, double-blind, placebo-controlled trials (Study 301 and Study 302) in 1,267 premenopausal women with HSDD, mostly in the US, who used bremelanotide 1.75 mg or placebo as needed for 24 weeks. Compared with placebo, bremelanotide produced statistically significant but modest improvements in both co-primary endpoints: the desire score on the Female Sexual Function Index rose by 0.35 points more (integrated analysis, on a 1.2–6.0 scale) and distress about low desire fell by 0.33 points more (on a 0–4 scale) ^[6][12]. There was no significant difference between groups in the number of satisfying sexual events, a secondary endpoint ^[12].

Women who completed the core phase could continue in a 52-week open-label extension: 684 of 856 eligible women enrolled and 272 completed it. Desire and distress scores continued to improve and no new safety signals were reported, although the extension had no placebo group ^[7].

The size and meaning of the benefit are debated. An independent 2023 re-analysis of RECONNECT data argued that the effect sizes on many trial outcomes were nil to small, that several outcomes registered on ClinicalTrials.gov had not been published, and that the questionnaires used have limited validation evidence in women with HSDD ^[10]. The trials were funded by the companies developing the drug ^[6].

Bremelanotide has more human data than almost any other peptide sold by research vendors. The development programme included about 3,500 people across 43 completed studies, with phase 3 participants taking it for up to 18 months ^[8]. The evidence base is, however, limited to specific populations: premenopausal women with a diagnosis of HSDD for the approved use, and earlier smaller studies in men. It has not been established as effective in postmenopausal women or in men, and the label says it is not indicated to enhance sexual performance ^[12].

The RECONNECT trials used 1.75 mg injected under the skin as needed, around 45 minutes before anticipated sexual activity ^[6][12]. Participants were told not to use more than one dose in 24 hours; the median number of doses in the 24-week controlled phase was 10, and most women used it two to three times a month ^[12]. The approved label recommends no more than one dose in 24 hours and no more than eight doses a month ^[12].

An earlier blood-pressure study compared 0.75, 1.25 and 1.75 mg subcutaneous doses ^[9]. Early men’s studies used intranasal doses, with effects seen above 7 mg ^[3], and the 2008 trial used 10 mg intranasally ^[4]. These are research and label doses for supervised or prescribed use, not guidance for unlicensed products whose content may differ.

In the integrated double-blind phase 3 data (1,247 women), the most common adverse events with bremelanotide compared with placebo were nausea (40.0% versus 1.3%), flushing (20.3% versus 1.3%), headache (11.3% versus 1.9%) and injection-site reactions (5.4% versus 0.5%). Nausea was the most common reason for stopping, and there were no deaths ^[8]. The label notes that nausea needed anti-sickness medication in 13% of patients and led 8% to stop, and usually improved with the second dose ^[12].

Bremelanotide causes small, transient increases in blood pressure and a fall in heart rate after each dose. In an ambulatory monitoring study of 397 premenopausal women, systolic pressure rose by about 2–3 mmHg relative to placebo in the first four hours, with peaks typically lasting under 15 minutes ^[9]. The label reports maximal increases of 6 mmHg systolic and 3 mmHg diastolic, peaking two to four hours after a dose and usually resolving within 12 hours. Vyleesi is contraindicated in uncontrolled high blood pressure or known cardiovascular disease ^[12].

Focal hyperpigmentation, including darkening of the face, gums and breasts, was reported in about 1% of patients using up to eight doses a month, but in more than a third of people given up to 16 consecutive daily doses; it did not always resolve ^[8][12]. The label also warns that bremelanotide can slow stomach emptying and substantially reduce blood levels of oral naltrexone, and advises effective contraception and stopping if pregnancy is suspected ^[12].

These safety data apply to the licensed product used as directed. Bremelanotide and melanotan II have both been identified in unlabelled products seized by police from the bodybuilding black market ^[14], and the purity and dose of unlicensed PT-141 cannot be assumed.

In the United States, bremelanotide is a prescription medicine, approved by the FDA on 21 June 2019 as Vyleesi for premenopausal women with acquired, generalised HSDD ^[11][12]. As of September 2026 we could not confirm a marketing authorisation for bremelanotide in the UK, the EU, Canada, Australia or New Zealand. Selling it as a medicine without authorisation, or with health claims, is generally unlawful in those countries; see our legal status overview and the pages for the UK and US.

The licensed Vyleesi autoinjector is stored at or below 25°C, must not be frozen and should be protected from light ^[12]. Research-grade PT-141 is usually supplied as a freeze-dried powder, which has different handling requirements once reconstituted; see our guide to storing peptides.

Research-grade PT-141 is not the licensed medicine. If you are comparing vendors, you can compare prices, check how to read a COA, and see which third-party tested suppliers publish independent results. Related peptides include melanotan II and kisspeptin-10, which is being studied for reproductive hormone and sexual-behaviour research.