PT-141 (bremelanotide): what it does, dosage, side effects and evidence

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].

Injected PT-141 was also tested in men. Under the skin, doses from 0.3 to 10 mg produced statistically significant erectile responses in healthy men at doses above 1.0 mg, without visual sexual stimulation, and 4 mg and 6 mg doses produced significant responses in men who reported an inadequate response to 100 mg Viagra ^[15]. In a crossover study of 19 men with erectile dysfunction who responded to Viagra or Levitra, a low 7.5 mg intranasal dose of PT-141 combined with 25 mg sildenafil gave a greater erectile response than sildenafil alone, with no new or more frequent side effects ^[16]. These were short laboratory studies measuring erections with a monitoring device, not trials of sexual satisfaction at home.

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].

Vyleesi’s label is narrow. It covers premenopausal women whose low desire developed after a period of normal desire, occurs in every situation and with every partner, and is not explained by another medical or psychiatric condition, a relationship problem or a medicine; it does not cover postmenopausal women ^[17]. An independent 2023 evaluation concluded that bremelanotide appears moderately safe and well tolerated but that its overall clinical benefit appears modest, while noting how hard it is to design trials in this area because of large placebo effects ^[24].

The most structured PT-141 reviews come from the RECONNECT exit study. Before entering the open-label phase, and while still blinded, 242 participants completed a survey and 80 of them a telephone interview. Women who had received bremelanotide described more sexual desire, physical arousal and better sexual activity with their partner, while women on placebo described benefits such as better communication and a positive experience of seeking treatment, without the physical responses ^[20]. The study was sponsored by the developers.

Online reviews of research-grade PT-141 nasal sprays and powders are a different matter: they cannot confirm what the product contained, and trial results for the licensed injection do not transfer to them.

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 programme also looked at other effects of melanocortin activation. In two small phase 1 trials in premenopausal women with obesity, bremelanotide given once, twice or three times a day for up to 16 days reduced calorie intake by about 400 kcal a day and body weight by 1.3 kg more than placebo; the studies were run by the developer and weight loss is not an approved use ^[22].

PT-141 started life as a nasal spray. The early men’s studies used intranasal doses ^[3], as did the 2008 sildenafil-failure trial ^[4] and a 2017 safety study that gave 20 mg intranasally with alcohol ^[21]. From the phase 2b study onwards, the women’s programme used injections under the skin ^[5][6], and the only approved product is a subcutaneous autoinjector containing 1.75 mg in 0.3 mL ^[17].

The label gives some numbers for comparison. Absolute bioavailability after the subcutaneous injection is about 100%, and a 20 mg intranasal dose produced a peak blood level about 2.5 times higher than the approved injection ^[17]. Injecting into the abdomen or the thigh made no significant difference to exposure, which is why the label names both sites ^[17]. By mouth, bremelanotide was barely absorbed in dogs ^[23], and there is no approved PT-141 pill.

No nasal PT-141 product has been approved anywhere we checked, and we did not find a published head-to-head trial of PT-141 nasal spray vs injection. PT-141 peptide powders and nasal sprays sold online have not been tested against the licensed medicine.

The label advises using the injection at least 45 minutes before anticipated sexual activity, but says the duration of efficacy after each dose is unknown and the best timing window has not been fully characterised ^[17]. Blood levels peak about an hour after the injection, and the PT-141 half-life is about 2.7 hours, ranging from 1.9 to 4.0 hours ^[17]. In the early intranasal studies in men, erections began around 30 minutes after dosing ^[3].

Side effects follow a similar timescale. The rise in blood pressure peaks two to four hours after a dose and usually settles within 12 hours ^[12], and nausea is most common with the first injection and usually lasts about two hours ^[17].

The two work in different places. Sildenafil, the active ingredient of Viagra, blocks the enzyme PDE5 in the penis, strengthening the effect of nitric oxide released during sexual stimulation; at recommended doses it has no effect without stimulation ^[18]. PT-141 acts on melanocortin receptors in the brain, and its mechanism for improving desire is not known ^[12].

Their approved uses differ too. Viagra is approved for erectile dysfunction in men, usually taken about an hour before sex and no more than once a day ^[18]. Vyleesi is approved only for premenopausal women with HSDD and is not indicated for men ^[17]. Viagra is contraindicated with nitrate medicines because together they can lower blood pressure dangerously ^[18], while Vyleesi raises blood pressure slightly and is contraindicated in uncontrolled hypertension or known cardiovascular disease ^[12].

The only published combination study found that low doses of the two together gave a greater erectile response than sildenafil alone in 19 men ^[16]. Studies in men who did not respond to Viagra are small, and the largest is under an expression of concern ^[4][15]. No trial has compared PT-141 with Viagra head to head as treatments.

Kisspeptin is a reproductive hormone rather than a melanocortin. In a 2023 randomised crossover trial at Imperial College London, 32 men with hypoactive sexual desire disorder completed two visits with a 75-minute intravenous infusion of kisspeptin-54 or placebo. Kisspeptin changed activity in the brain’s sexual-processing network while the men watched sexual videos, increased penile tumescence by up to 56% more than placebo and increased some measures of desire, such as happiness about sex ^[19].

That trial tested a single infusion in a laboratory, used the 54-amino-acid form rather than the shorter kisspeptin-10 sold online, and did not measure sexual activity at home. PT-141 has far larger trials, but in women. There is no head-to-head comparison of kisspeptin vs PT-141.

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.

There is no approved PT-141 dosage for men. The men’s studies used 0.3 to 10 mg under the skin ^[15] and intranasal doses such as 7.5 mg with sildenafil ^[16] or 10 mg alone ^[4]. The label notes that blood levels rise less than proportionally between 0.3 and 10 mg and reach a plateau at a 7.5 mg injection, about 4.3 times the maximum recommended dose ^[17], so larger amounts do not produce proportionally more drug in the blood.

For the arithmetic of research vials, a 10 mg vial mixed with 2 mL of liquid contains 5 mg per mL, which is 50 µg in each 0.01 mL, one unit on a U-100 insulin syringe. Our peptide calculator does this for other vial sizes and volumes, and our guide to bacteriostatic water covers the diluent. The licensed autoinjector avoids this step entirely, and a calculator cannot confirm how much peptide an unlicensed vial holds.

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].

Other PT-141 side effects and downsides come from the clinical pharmacology studies. In a crossover study with alcohol, a 20 mg intranasal dose did not interact with alcohol pharmacokinetically and caused no significant drop in blood pressure on standing, although flushing was more common when bremelanotide was combined with alcohol than with alcohol alone ^[21][17]. Exposure rose twofold in people with severe kidney impairment and 1.7-fold with moderate liver impairment ^[17]. Animal studies found effects on pregnancy in dogs, and too few pregnancies occurred in trials to judge the risk in people ^[17].

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.

In the US, Vyleesi is now marketed by Cosette Pharmaceuticals, whose current label keeps the same indication and 1.75 mg dose ^[17]. The FDA does not accept “research use only” labelling as a defence for PT-141 sold for human use: an August 2026 warning letter to Royal Peptides LLC listed PT-141 among the products it said were intended to be drugs despite that labelling ^[25].

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.

Country pages list PT-141 prices in the UK and in the US. Bremelanotide and melanotan II have both turned up in unlabelled black-market products ^[14], so it is worth checking for an independent third-party test and reading how to spot a fake peptide supplier before relying on any vendor.