PT-141: The Definitive Guide

What is PT-141?

PT-141 is bremelanotide, a lab-made peptide that acts on the brain's melanocortin receptors. As Vyleesi it is an FDA-approved injection for premenopausal women with hypoactive sexual desire disorder (HSDD), meaning persistently low sexual desire that causes distress. Research vials sold online as PT-141 are not that medicine. [1], [2]

PT-141 was the development code of Palatin Technologies, the company that developed it from Melanotan II, a tanning peptide studied at the University of Arizona. It is a ring of seven amino acids (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH), with the molecular formula C50H68N14O10 and a molecular weight of 1,025.2. [3], [1], [4]

The FDA approved Vyleesi on June 21, 2019, as a 1.75 mg single-use autoinjector. It was the second medicine approved for HSDD, after the daily tablet flibanserin (Addyi) in 2015. The label says it is not for HSDD in women after menopause or in men, and not for improving sexual performance. Cosette Pharmaceuticals has owned it since December 2023. [2], [5], [6], [1], [7]

Most people who look it up are not women with a diagnosis of HSDD. Men and women buy PT-141 as a "libido peptide" or for erections, often as a freeze-dried powder that is mixed with water and injected, or as a nasal spray. Those uses, doses and products were not what the trials tested. [8], [9], [10]

Typical PT-141 Protocols

The approved dose is one 1.75 mg subcutaneous injection, used only when needed, at least 45 minutes before sex, no more than once in 24 hours and not more than eight times a month. There is no starting dose, no titration and no cycle: every dose is 1.75 mg. The label adds that how long each dose works is unknown, and that people can choose their own timing based on how long the effect lasts for them and on side effects such as nausea. [1]

In the trials, women injected a median of 10 times over 24 weeks, and most used it two to three times a month and no more than once a week. The label advises against more than eight doses a month because few trial participants went above that, and because more frequent dosing raises the risk of skin darkening and lengthens the time each month when blood pressure is raised. [1]

What schedules do protocol websites describe?

Outside the approved product, PT-141 is sold as a research powder in vials, usually 10 mg, that is mixed with sterile water and injected with an insulin syringe. These schedules come from clinic, seller and dosing websites, not from trials.

The most common pattern in the reviewed dosing sources is 1–2 mg (1,000–2,000 mcg) by subcutaneous injection, used as needed before sex, no more than once in 24 hours, often after a lower first dose. Of 18 independent sources that give a subcutaneous amount, 17 include an amount between 1 and 2 mg, and 10 print the labeled 1,750 mcg. All but one use it before sex rather than on a daily schedule. [12], [8], [13], [14], [15], [16]

Titration Changing the amount in steps

The label has none: every dose is 1.75 mg. Many websites instead start with a lower test dose (about 7 of the 18 publishers that give an injected amount) to check for nausea and a blood-pressure response, then move up on later occasions if it is tolerated: for example 500 mcg first, then 1,000–1,750 mcg; or 1,000 mcg, then 1,500 mcg, then 2,000 mcg; or a 1,000 mcg test dose, then the labeled 1,750 mcg. Some pages start as low as 250 mcg. [1], [12], [8], [13], [14]

Breaks and cycles

Not applicable to the label, which uses it only when needed, with a monthly limit and a stop rule after 8 weeks without improvement. Most dosing pages also describe as-needed use with no cycle. A few add rules the label does not have, such as 72 hours between doses, no more than twice a week, or 4–8 weeks of use followed by 4 weeks off. No study has tested a break schedule. [1], [13], [17], [18]

Read the units: mcg means micrograms; 1 mg equals 1,000 mcg, so the labeled 1.75 mg is 1,750 mcg. Each amount above is one dose, used on a single occasion, not a daily total. Nasal sprays and troches (lozenges) are left out of this table because their amounts cannot be compared with injected ones (see routes).

Low, mid and high are alternatives, not steps to move through, and each row keeps its source's amounts, timing and limits together. The label dose comes from trials in premenopausal women; the website rows come from protocol sources, not clinical trials, and most of them are written for men. The cited references give the full details.

Cautions for every schedule above.

• Heart and blood pressure. The label rules out PT-141 with uncontrolled high blood pressure or known heart or blood-vessel disease, because blood pressure rises for several hours after each dose. [1]
• Nausea. 40% of women in the trials had nausea at the labeled dose, and ondansetron taken beforehand did not prevent it. [1], [19]
• Skin darkening. Daily use caused dark patches in 38% of people within 8 days, and they did not always fade. [1]
• Long erections. Men describe erections lasting many hours, often alongside Viagra-type drugs; one lasting more than four hours is a medical emergency (priapism). [20]
• Pregnancy and product quality. Not for use in pregnancy, with no information on breastfeeding. Research vials have no guaranteed content, strength or sterility. [1], [21]

People with heart disease or high blood pressure, anyone who is pregnant, breastfeeding or under 18, people with severe kidney or liver disease, and anyone taking naltrexone tablets should read who should be especially cautious first.

Where protocols differ: test doses, timing, daily schedules and nasal sprays ↓

What is PT-141 commonly used for?

Most people who look up PT-141 want more sexual desire or better erections. It has one approved use, low sexual desire in premenopausal women, and a much wider set of uses online: men's libido and erections, couples using it together, and low desire while taking antidepressants or weight-loss drugs. [1], [10], [27]

How much evidence stands behind each of these differs a great deal. The approved use rests on large placebo-controlled trials; the others rest on small early studies, company press releases or personal accounts. [22], [28], [29]

Low sexual desire in premenopausal women (the approved use)

HSDD means low sexual desire that has lasted for months, causes the person distress, and is not better explained by another medical or mental-health condition, a medicine, or problems in the relationship. Vyleesi is approved only for the acquired, generalized form: low desire that developed after a period of normal desire and happens regardless of the situation or partner. [1]

In two 24-week trials of 1,247 premenopausal women, those using PT-141 reported a small increase in desire and a small drop in distress about low desire compared with placebo. The number of satisfying sexual events did not increase more than with placebo. See what the trials found for the numbers and the debate about what they mean. [22], [1]

Does PT-141 boost libido in anyone who takes it?

No trial has shown that. The approved use is a diagnosis made after other causes are ruled out, in women before menopause, and the label says it is not for enhancing sexual performance. The label says it is not indicated for women after menopause, and the FDA review notes its safety has not been established in that group. [1], [6]

In public forums, people who use it without that diagnosis describe everything from a strong effect to nothing at all. Many men describe erections without any extra desire, and many women describe physical genital arousal without feeling more interested in sex. [30], [31], [32]

Erections and low desire in men

PT-141 was first developed for men with erectile dysfunction. In small studies, subcutaneous doses of 0.3–10 mg produced erections in healthy men at doses above 1 mg, and 4 or 6 mg produced erections in men whose erections did not respond well to Viagra. Nasal sprays produced erections at doses above 7 mg, about 30 minutes after dosing. [28], [33]

A 2008 trial randomized 342 men whose erections had not responded to sildenafil to a 10 mg nasal dose or placebo. It reported positive results in 34% on the drug versus 9% on placebo, but the journal attached an expression of concern to that paper in 2023. No approval for men followed, and the label says it is not indicated for men. [34], [35], [1] The FDA's reviewers noted that erections are an expected effect of this drug class in males. [6]

Low desire on antidepressants or weight-loss drugs

This is one of the most common reasons people online say they try PT-141, but it has not been studied. The only trial data involving antidepressants measured drug levels: in healthy women, PT-141 did not meaningfully change blood levels of sertraline or venlafaxine. That says nothing about whether it helps sexual side effects. [36], [29], [37]

People in public forums often discuss it for low desire during weight-loss treatment with drugs such as tirzepatide or retatrutide. Those drugs can also cause nausea, which makes PT-141's most common side effect harder to judge. No study has tested PT-141 for this. [38]

Other uses you may come across

• Weight loss. In one phase 1 trial, women with obesity who injected PT-141 three times a day for 16 days lost about 1.3 kg more than with placebo; a second, 4-day crossover trial also found greater weight loss (85 women across both). A company-run 8-week study reported 4.4% weight loss with PT-141 plus tirzepatide versus 1.6% with placebo; against tirzepatide alone, 40% versus 27% reached 5% weight loss. These are press-release figures, and the registry has no posted results. [39], [40], [41]
• Kidney disease. In a 16-person open-label study in diabetic kidney disease, 4 of 7 people with data had at least a 30% drop in protein in the urine. An earlier company press release had said 71%. [42], [43]
• Tanning. Skin darkening is a side effect, not an intended use. Some people online notice they tan; others stop because of it. [1], [44]

None of these is an approved use.

Where do PT-141 protocols differ?

The recurring amounts are easy to list. Here is where sources disagree, and what that means when reading a schedule.

The label dose or a lower "test dose"?

The label has one dose, 1.75 mg, from the first injection. Many dosing websites and clinics (about 7 of 18) start lower, at 250–1,000 mcg, mainly to see how bad the nausea is. Community education groups go lower still, often suggesting 100–500 mcg for a first try, below any dose tested in the trials. The phase 2b trial tested 0.75, 1.25 and 1.75 mg, and the label found nausea most common after the first dose. [1], [12], [14], [45]

People online who started low describe both outcomes: some had no side effects and no effect, and raised the dose; others were already sick at 100–333 mcg. [46], [47], [48]

As needed, or on a schedule?

This is where sources disagree most. The label, the trials and most websites describe use only before sex. Three sites copy the same schedule of daily injections for 16 weeks, rising from 500 to 1,000 to 1,500 mcg a day; that is up to 112 doses, against a label limit of eight a month. Others add fixed spacing, such as a dose every 72 hours or no more than twice a week, or a scheduled 4–8-week course. [23], [24], [25], [17]

Daily dosing is the pattern the label warns about. In a study where women took PT-141 every day, 38% developed dark skin patches after 8 days and another 14% after 8 more days. Blood pressure did not keep climbing with daily doses, but it was raised for part of every day. Community education groups also describe members dosing every 4 days or three times a week, and some of those members report skin darkening. [1], [49]

How long before sex?

The label says at least 45 minutes, and websites range from 30 minutes to 2 hours. But the FDA noted that the best timing has not been worked out, and people online very often describe the main effect arriving 2–12 hours after the injection, sometimes the next morning. [1], [11], [8], [30], [50], [51]

Blood levels peak about an hour after an injection, so a delay of many hours is not explained by how the drug is absorbed. Nobody knows why reports differ so much from the label. Several people advise testing it on a free day rather than before a planned occasion. [1], [52]

Do men and women use the same dose?

The only tested and approved dose is for women: 1.75 mg. Websites give men 1–2 mg, often with the claim that men need a longer wait before sex. Some pages and forum posts say men should use less than the labeled dose because erections can last too long; others give men up to 2 mg or more. No trial has compared doses in men with the approved schedule. [8], [13], [30], [46]

How high do sources go?

Most pages stop at 2 mg per dose, and one gives that as a ceiling because higher doses add nausea and blood-pressure effects without more benefit. One clinic splits 2 mg into two 1 mg injections 30 minutes apart, one page says 1.75–3 mg, and one clinic flyer gives 4 mg to men whose erections did not respond to sildenafil, which echoes the early male studies. The label says nausea, skin darkening and larger blood-pressure rises are more likely at higher doses. [12], [18], [53], [26], [28], [1]

Does an anti-nausea drug beforehand help?

Many websites and community education groups recommend taking ondansetron (Zofran) before PT-141. In the one controlled test, 228 healthy women took 8 mg of ondansetron or a placebo 30 minutes before 1.75 mg of PT-141, and it did not reduce nausea. The patient leaflet says ondansetron beforehand is not recommended, and that a doctor may prescribe an anti-nausea medicine to take after nausea starts. [13], [14], [19], [1]

People online report mixed results: some say ondansetron, ginger, an antihistamine or a snack helped, while several women say they vomited despite ondansetron. Splitting the dose, or injecting at bedtime to sleep through the nausea, are common tactics that have not been tested. [54], [55], [56], [57]

Are nasal sprays and troches the same protocol?

No. Their amounts cannot be converted into injected doses. The nasal form was dropped from development because absorption through the nose varied too much, and no human study has measured troches. See how route changes exposure. [6]

How do milligrams convert to syringe units?

Research PT-141 is usually sold as a 10 mg powder that is mixed with sterile water (reconstitution). On a U-100 insulin syringe, units measure volume, not drug. For example, 10 mg mixed into 2 mL gives 5 mg (5,000 mcg) per mL, or 50 mcg per unit, so 1.75 mg would be 35 units. The same 1.75 mg is 53 units if the vial is mixed with 3 mL. Doserly's reconstitution calculator works this out for any vial and shows each step. [58], [59]

Unit mix-ups appear in public accounts, such as a stated "50 mg" first dose that was almost certainly 50 mcg, or doses given in "units" without the vial strength. [60], [61]

What happens when you stop PT-141?

For most side effects, nothing lasting: blood pressure returns to its starting level within about 12 hours of each dose. The exceptions are skin darkening, which may not fade completely, and reports of low desire after use, which have not been studied. [1]

• The effect itself. Each dose is taken on its own, so there is no course to stop. The label says to stop after 8 weeks if there has been no improvement. The 52-week extension of the trials did not follow people after they stopped. [1], [62]
• Dark patches. Resolution was not confirmed in all patients after stopping. People online describe darkening that lasted weeks to months. [1], [63], [64]
• A "crash" afterwards. Some men and women describe a day to up to two weeks of low desire, weaker erections or low mood after an effective dose, and a few describe weeks of low desire or numbness after stopping. No study has looked for withdrawal effects or a rebound, and several of these people were also using other drugs. [65], [66], [67], [68]
• Pregnancy. The label advises stopping if pregnancy is suspected and using effective contraception while taking it. [1]

Do the autoinjector, research vials, nasal sprays and troches behave the same way?

No. The approved injection has been measured carefully in people; the other forms mostly have not. [1]

• Subcutaneous autoinjector. Absorption is essentially complete (bioavailability about 100%), blood levels peak about 1 hour after the injection (range 0.5–1 hour), and injecting in the abdomen or thigh made no meaningful difference. The autoinjector gave the same blood levels as a prefilled syringe. [1], [79]
• Research vials, injected. If the vial really holds bremelanotide at the stated strength, an injection should behave like the approved one. That is the uncertainty: research products have no guaranteed identity, strength or sterility, and an FDA inspection found one compounded product at 114% of its labeled strength. [80], [21]
• Intranasal spray. PT-141 was first developed as a nasal spray. In men it peaked in the blood at about 30 minutes, with a half-life of about 1.85–2.09 hours, but the FDA's review says development switched to injections because the amount absorbed through the nose varied too much. The developer linked that variable absorption to the blood-pressure rises and stomach effects seen with the spray. [33], [6], [81]
• Troches and other mouth forms. In dogs, very little PT-141 was absorbed by mouth. No human study has measured a troche, a tablet held against the gum or under the tongue. [82]

Doserly

What happens in the 12 hours after one 1.75 mg injection

Blood level

Peaks about 1 hour after the injection (range 0.5–1 hour), then halves about every 2.7 hours (range 1.9–4.0).

Nausea (40% of women)

Often starts within the first hour and lasts about 2 hours.

Blood pressure

Rises by up to 6/3 mmHg on average, peaking 2–4 hours after the dose, and is usually back to baseline within 12 hours. Heart rate falls by up to 5 beats a minute.

Reported effect (personal accounts)

Many people describe the effect arriving 2–12 hours after injection. This is not a measurement.

Blood levels, nausea and blood pressure follow a short, predictable course after each dose. The label says to inject at least 45 minutes before sex; many people describe the effect arriving later than blood levels would suggest.

Timings from the US Vyleesi label and FDA review. The reported-effect band is from public personal accounts, not a measurement.

What amounts do nasal sprays and troches use?

These are the amounts sellers and clinics state. None has been tested, and "per spray" strengths differ so much that the numbers cannot be compared.

The blend troche adds tadalafil (Cialis), an erection drug, and oxytocin, a hormone, so its effect cannot be credited to PT-141. People online mostly describe nasal sprays as doing nothing, or far less than an injection, and some burned. [54], [86], [47], [87]

How long does PT-141 stay in the body?

Only hours. After an injection, the level in the blood falls by half about every 2.7 hours (range 1.9–4.0 hours), and in a study with a radioactive tracer, 88% of the dose had left the body in urine and feces within 8 days. [1], [88]

The effect is a different question. The label says how long each dose works is unknown, and many people online describe effects lasting into the next day or two. The drug's half-life does not explain that, and no study has measured it. [1], [89], [27]

Does it matter where it is injected?

For the approved product, no. The label found no meaningful difference in drug levels between the abdomen and the thigh. This guide does not cover injection technique; the Academy note below points to practical handling basics. [1]

How should PT-141 be stored, and how long does it last?

For the approved autoinjector, the label is clear. For research powder and mixed vials, nobody knows, because no stability study exists for them.

• Vyleesi autoinjector. Store at or below 25 °C (77 °F), do not freeze and protect from light. The FDA accepted a shelf life of 36 months for the sealed product. Do not use it if the liquid is cloudy, discolored or has particles. [1], [90]
• What breaks it down. A 2026 laboratory study found bremelanotide is especially sensitive to oxidation and is also damaged by heat and light, forming eight breakdown products. [91]
• Powder and mixed vials. Dosing pages advise a fridge at 2–8 °C after mixing and give limits of 28 or 30 days, and some say to protect it from light. None cites a stability test for PT-141 in a mixed vial. [25], [13], [70], [23]
• What people report. Accounts conflict: some say a refrigerated vial still worked after months, while one person found the same dose did nothing from a vial two weeks later. Neither tested the vial's strength. [87], [89]

No data were found on how long an opened nasal spray or a compounded troche keeps its strength.

What do we actually know about PT-141 in people?

A lot more than for most peptides sold online. PT-141 went through a full drug-development program: a company safety review counts about 3,500 people in 43 completed studies. What has not been tested is how most people use it now: in men, after menopause, from research vials, as a nasal spray or troche, or on a schedule. [92], [1]

What did the trials in women find?

A separate 2008 trial of PT-141 in women with arousal disorder was retracted by its journal because the author did not respond to questions about the data, so this guide does not use its results. [96]

How big is the benefit?

Small on average, and the size is argued over. Desire was scored from 1.2 to 6 on the Female Sexual Function Index. In the two trials, the average score rose by 0.5–0.6 points with PT-141 versus 0.2 with placebo; distress about low desire, scored from 0 to 4, fell by 0.7 versus 0.4. After allowing for placebo, that is about a third of a point on each scale. [1], [22]

Doserly

RECONNECT results drawn to scale

Desire score (1.2–6)

Average rise of 0.5 with PT-141 vs 0.2 with placebo (Study 1) and 0.6 vs 0.2 (Study 2): about a third of a point more than placebo.

Distress about low desire (0–4)

Average fall of 0.7 with PT-141 vs 0.4 with placebo in both studies.

Satisfying sexual events per month

0.0 with PT-141 vs −0.1 with placebo (Study 1) and 0.0 vs 0.0 (Study 2): no difference.

On each scale the average improvement with PT-141 was only a little larger than with placebo, and satisfying sexual events did not change.

Mean change from baseline to end of the 24-week double-blind period (modified intent-to-treat), US label Tables 2–4.

Supporters point to a responder analysis: when women were asked whether they had benefited, 58% on PT-141 and 35–36% on placebo said yes. They also point to a strong placebo response, typical of trials that rely on how people feel; across female sexual dysfunction trials, placebo raised sexual function scores by 3.62 points. [22], [97]

Critics point elsewhere. Satisfying sexual events changed by 0.0 with PT-141 in both trials, against −0.1 and 0.0 with placebo, differences the trials could not tell apart from chance. An independent reanalysis found that 8 of 11 registered efficacy outcomes had not been published and that the questionnaires used have weak evidence of measuring what matters to women with HSDD. The Drug and Therapeutics Bulletin concluded that PT-141 added no enjoyable sexual experiences, and a 2023 expert review called the benefit modest. The trial investigators published a rebuttal. [22], [98], [5], [99], [100]

Dropouts complicate the picture too. More women stopped early on PT-141 than on placebo (40% versus 13% in one trial, 39% versus 25% in the other), and one reanalysis estimated that for every 6 women treated, one more stopped because of side effects than would have on placebo. [1], [101]

What did the studies in men find?

A 2023 case report describes a young man with lifelong inability to reach orgasm for whom PT-141 did not help, and one attempt caused penile pain. [102]

What didn't these studies test?

• Men using it at home for low desire, or on the as-needed 1–2 mg schedules websites describe (1–2 mg was given to men only as single laboratory doses).
• Women after menopause; the label says it is not indicated for them, and the FDA review notes safety there is not established.
• Research vials, nasal sprays or troches bought online.
• Use more often than the label allows, apart from short daily-dosing safety studies.
• Low desire caused by antidepressants or weight-loss drugs.
• Pregnancy, breastfeeding (a milk study has no posted results), people under 18 or over 65. [6], [76], [1]

How does PT-141 work?

PT-141 switches on several melanocortin receptors, the sensors that respond to the body's own melanocyte-stimulating hormones. In order of strength, it acts on MC1R, MC4R, MC3R, MC5R and MC2R; at the approved dose, MC1R and MC4R matter most. The label is direct about the rest: how it improves HSDD in women is unknown. [1]

MC4R is found in many parts of the brain, including the hypothalamus, which helps control sexual behavior, appetite and hormones. The leading idea is that PT-141 acts there rather than on blood flow in the genitals. Most of the support comes from animals: in rats, PT-141 activated nerve cells in the hypothalamus; in female rats, it increased behaviors that invite mating without changing other sexual behaviors; and reviews propose that it releases dopamine in a hypothalamic area called the medial preoptic area. [1], [103], [104], [105], [106]

Not every animal result points the same way. In a 2025 study in female hamsters, PT-141 did not act on the brain's reward circuit and did not make sex more rewarding. In people, the only direct evidence is the brain-imaging study in 31 women, which showed changed responses to sexual images. [107], [94]

How is it different from Viagra-type drugs?

Viagra (sildenafil), Cialis (tadalafil) and similar drugs are PDE5 inhibitors: they widen blood vessels in the penis so an erection can happen when a man is aroused. PT-141 is thought to work in the brain. In rabbit vaginal tissue in the laboratory, it did not relax the blood-vessel or vaginal muscle at the one concentration tested, while the natural hormone did. [108] In healthy men it produced erections without sexual images, and the FDA notes erections are an expected effect in males; that fits a brain-level action but does not prove it. Men online also describe erections appearing without any sexual trigger. [28], [6], [109]

Why does it darken skin?

MC1R sits on melanocytes, the skin's pigment cells, and switching it on makes them produce melanin. That is the same receptor Melanotan I and Melanotan II use to tan the skin. With PT-141 the darkening tends to appear in patches, on the face, gums and breasts, and more often in people with darker skin. [1], [6]

Why does it cause nausea and flushing?

Nobody has shown exactly why. An FDA reviewer suggested the vomiting may relate to MC3R, which is found in the brain and gut, and the nonclinical review found nausea, vomiting and skin darkening were the main effects at lower doses across animal species. Nausea is worst with the first dose and eases for most people with later doses. [6], [1]

Is PT-141 a metabolite of Melanotan II?

Not in any way that matters for use. PT-141 is the same ring of seven amino acids as Melanotan II, but it ends in an acid where Melanotan II ends in an amide; the label describes it as a peptide "with a free acid at the carboxyl terminus." A 2020 mouse study found a breakdown product of Melanotan II with that structure in tissue, and some published papers and education materials repeat the "metabolite" idea. Nobody has measured how much forms in people, and PT-141 was developed, tested and dosed as its own drug. [6], [110], [20], [1]

What are the risks and unanswered questions?

Is PT-141 safe?

The approved autoinjector has a well-documented safety record in premenopausal women using it as the label allows: side effects are common but mostly mild to moderate and brief, and serious side effects were rare. Use outside the label is a different, largely untested situation. [1]

In the trials, 71% of side effects were mild or moderate, and serious adverse events happened in 1.1% of women on PT-141 versus 0.5% on placebo. But 18% stopped because of side effects, versus 2% on placebo. The FDA concluded that the benefits outweigh the risks when it is used according to the label. [1], [6]

What side effects did the trials find?

In the two phase 3 trials, these were reported in at least 2% of women and more often than with placebo:

Source: US label, Table 1. [1]

Nausea usually started within an hour and lasted about two hours. It affected 21% of women after the first dose and about 3% after later doses. In total, 13% needed anti-nausea medicine and 8% stopped because of it. A company safety review that grouped injection-site reactions more narrowly reported 5.4% versus 0.5%. [1], [92]

What happens to blood pressure and heart rate?

Blood pressure rises briefly after every dose. In the trials the largest average rise was 6 mmHg in the top number (systolic) and 3 mmHg in the bottom number (diastolic), peaking 2–4 hours after the dose, with heart rate falling by up to 5 beats a minute. Both were usually back to normal within 12 hours. [1]

In a study of daily doses, all-day ambulatory monitoring showed an average daytime rise of 1.9/1.7 mmHg after 8 days, and the effect did not add up with repeated daily doses. That is why the label rules it out with uncontrolled high blood pressure or known heart or blood-vessel disease, and asks prescribers to check heart risk before starting and from time to time. [1], [49], [111]

People online occasionally report higher readings or a racing heart: one described a jump from 110/60 to 130–140/70–80 for an hour or two, and another a heart rate of 140–150 after a first 1 mg dose (with oxytocin the same night). These are single, unmeasured accounts with unknown products. [66], [112], [61]

Why do dark patches appear, and do they go away?

Focal hyperpigmentation, meaning dark patches in small areas, affected 1% of women using up to eight doses a month, on the face, gums and breasts. With daily dosing it affected 38% within 8 days and another 14% after 8 more days. People with darker skin were more likely to be affected, and the patches did not fade in everyone after stopping. The label suggests considering stopping if it happens. [1]

This matters because many people online dose far more often than the label allows; see what people report about darker skin and moles. The label reports no link to moles or skin cancer, and none has been studied. [1]

What is known about erections that last too long?

In men, erections are an expected effect of drugs like PT-141, and the published male studies (single doses in small groups) described it as well tolerated. We found no published case of priapism with PT-141 itself. [6], [28], [33] Men online do describe erections lasting many hours; those accounts are summarized in what people report.

Its close relative Melanotan II has caused priapism needing drainage or surgery, in one case an erection that had lasted 30 hours after a 2 mg injection, and the FDA lists priapism among the serious events reported with it. Men using PT-141 in public forums describe erections lasting 6–12 hours or more, painful erections, and one emergency-room visit for an 8-hour erection while also taking Cialis. Community education groups report the same pattern, often at 1.5–2 mg or with tadalafil. An erection lasting longer than 4 hours is a medical emergency. [20], [113], [114], [54], [115], [116]

What other rare problems have been reported?

• Liver. In the extension study, one woman developed acute hepatitis (liver inflammation) after 10 doses over a year; a role for PT-141 could not be ruled out. [1]
• Kidneys and liver disease. Drug levels doubled in severe kidney disease, so the label urges caution there; it has not been tested in severe liver disease. [117], [1]
• Heart rhythm. A dedicated study at 5 and 20 mg by nasal spray found no meaningful effect on the heart's QT interval. [6]
• Misuse. In a study designed to detect abuse potential, responses were not significantly different from placebo. [118]

Could product quality change the risk?

Yes. Police-seized black-market samples sold to bodybuilders were identified as Melanotan II and bremelanotide, showing both circulate outside medicine supply chains. The FDA found a compounded bremelanotide injection containing 114% of its labeled amount, and in August 2026 it sent warning letters to five companies selling "research" PT-141. People online repeatedly suspect vials of being fake or weak after getting no effect at 2 mg. [21], [80], [119], [55], [120]

Is PT-141 legal? Is it FDA-approved?

Checked September 24, 2026. Rules differ by country and change quickly. A "research use only" label does not make a product legal to sell or safe to use.

United States. Bremelanotide is FDA-approved as Vyleesi (June 2019), a prescription autoinjector for premenopausal women with acquired, generalized HSDD. Nothing else is approved. On August 24, 2026, the FDA sent warning letters to Peptide Partners, Royal Peptides, Tex Peptides, NuScience Peptides and Peak Performance Peptides naming PT-141, and earlier letters named compounded bremelanotide (2019 and 2020). Bremelanotide is not on the FDA's lists of nominated bulk substances for compounding; as an ingredient of an approved drug it can meet one of the conditions for pharmacy compounding, which does not by itself make a product legal. [2], [1], [119], [121], [122], [123], [124], [125], [126], [127], [128]

Canada. We found no Vyleesi or bremelanotide product in Health Canada's Drug Product Database. Health Canada advisories in April 2025 and August 2025 list PT-141 and bremelanotide among seized, unauthorized injectable peptides. [129], [130], [131]

Australia. Bremelanotide has no named entry in the June 2026 Poisons Standard. In a 2019 Federal Court case against a peptide clinic, the medicines regulator argued that bremelanotide was already a prescription-only (Schedule 4) substance through its relationship to afamelanotide and Melanotan II; that was the regulator's argument, not a ruling. Melanotan II has been Schedule 4 since 2018. [132], [133], [134]

European Union and United Kingdom. We found no authorization in the European Medicines Agency's medicines data, and could not confirm the UK position. [135]

China and South Korea. The developer reported a first commercial sale in China in 2023 through Hainan's special medical zone, without national registration. A Korean phase 3 trial was completed in 2023, and a February 2026 Korean news report said the Korean licensee had withdrawn its approval application; we could not confirm this with the Korean regulator. [136], [77], [137]

Is PT-141 banned in sport? Does it show up on a drug test?

It is not named on the World Anti-Doping Agency's 2026 list or on the 2027 list published in September 2026. The list's S0 category covers substances with no approval for human use anywhere; bremelanotide is approved in the United States, so that rule does not obviously apply, but no anti-doping body has ruled on it, and a research product could contain something else. Athletes should check with their anti-doping organization. No published study has measured how long it can be detected. [138], [139]

Who should be especially cautious?

• People with high blood pressure or heart disease. The label rules it out with uncontrolled high blood pressure or known heart or blood-vessel disease. [1]
• Pregnancy. Not recommended: the label advises effective contraception and stopping if pregnancy is suspected, and animal studies showed harm to offspring at multiples of human exposure, and the lowest harmful dose was not identified. [1]
• Breastfeeding. There is no information on whether it passes into milk; a completed study has not posted results. [1], [76]
• Under 18, and older adults. Safety and effectiveness are not established in either group. This guide is written for adults. [1]
• Severe kidney or liver disease. Use with caution; side effects such as nausea and vomiting may be more frequent and severe. [1]
• People with darker skin, or anyone planning frequent use. Skin darkening is more likely and may not fade. [1]
• Men, especially with Viagra-type drugs. Not approved for men; prolonged erections are the main concern (see above).
• People taking other medicines, and drug-tested athletes. See the interactions below and the sport section above.

Has PT-141 been tested alongside other medicines?

Some combinations have been tested for drug levels, and the results matter:

• Naltrexone tablets. PT-141 cut blood levels of oral naltrexone by 64% at their peak and 40% overall. The label says to avoid PT-141 with naltrexone tablets taken for alcohol or opioid dependence, because treatment could fail. [36], [1]
• Other tablets. PT-141 slows stomach emptying, which can delay or reduce absorption of medicines taken by mouth. The label advises avoiding it with oral drugs that need a steady level to work, such as antibiotics, and notes a delayed effect of pain relievers such as indomethacin. [1], [140]
• Alcohol. With a 20 mg nasal dose (about 2.5 times the peak level of the approved injection), alcohol did not change drug levels. Headache was more common with the combination than with PT-141 alone, and flushing more common than with alcohol alone. [141], [1]
• Viagra-type drugs. Only one small combination study exists, using a nasal dose with a low dose of sildenafil. Many people online combine injected PT-141 with tadalafil, and most reports of erections lasting too long involve that combination. [75], [142], [54]
• Melanotan II, oxytocin, kisspeptin and other peptides. None of these combinations has been studied. [27], [143]

Bring a complete list of everything you take to a pharmacist or doctor.

What should be monitored while using PT-141?

For the approved product, the label sets out what to watch. For research products there is no official plan; what follows is what the label and studies measured, useful for preparing questions for a clinician. It is not a personal testing plan.

What does the label ask for?

• Heart risk and blood pressure. Consider heart risk before starting and from time to time during treatment, and make sure blood pressure is well controlled. [1]
• Whether it is working. Stop after 8 weeks if symptoms have not improved. [1]
• Skin. Consider stopping if dark patches develop. [1]
• Nausea. Consider stopping for persistent or severe nausea, or anti-nausea treatment for people who are bothered but want to continue. [1]

No blood tests are required by the label.

What did the studies measure?

The trials measured blood pressure and heart rate in the clinic and, in dedicated studies, around the clock; heart rhythm (ECG); liver tests, after the hepatitis case; skin changes; and desire, distress and satisfying sexual events with questionnaires and diaries. [6], [49], [111], [1]

Which signals matter, and why?

Some signals need prompt medical care rather than tracking. An erection lasting more than 4 hours needs emergency care; prolonged erections have been reported with the closely related Melanotan II. [20] As general safety advice for any injected drug, not a warning from the PT-141 label, chest pain or signs of a severe allergic reaction such as swelling of the face or throat or trouble breathing also need urgent care.

Most of these come from the label for the approved product, not from monitoring studies of research vials, so they show what regulators have flagged rather than what a person will experience.

What do people in public communities report?

Public forums describe PT-141 as unpredictable: a strong effect for some people, nothing for others, and side effects that decide whether many try it twice. The most useful posts say how much was taken, from what product, what else was used, and what happened the next day. These are selected discussions, not a survey of everyone who has tried it, and most come from men using research vials, a group the trials did not study. [54], [50], [10]

What do the positive reports look like?

The typical success story comes from a man who, after a lower dose did little, found an amount that worked: one 42-year-old felt nothing at 500 mcg but got the effect he wanted at 1.5 mg a week later, with a hangover-like feeling the next morning. Another injected 0.7 mg at 4 a.m. and felt strong desire from about 9 a.m. to 3 p.m. Some men with erectile dysfunction describe it working where Viagra-type drugs failed; a 70-year-old described it working every time. [46], [144], [50], [145]

Women's success stories more often describe genital sensitivity, lubrication or stronger orgasms. A postmenopausal breast-cancer survivor who had stopped hormone therapy called prescribed Vyleesi a "godsend", and a 62-year-old woman was described as highly aroused at 1.4 mg with no nausea. Couples describe using it together. [146], [147], [148]

How long does it take, and how long does it last?

Much longer than the label's 45 minutes, in most accounts. People describe the effect starting 2–12 hours after the injection: "four to eight hours", "about six or seven hours later", effects beginning at 2–3 hours and peaking at 5–6 hours in a 53-year-old woman. One woman on prescribed Vyleesi felt nothing at 45 minutes, then a strong effect within 2 hours that lasted all day. [109], [30], [51], [149]

Effects often last into the next day or two. Arrival at awkward times, at work or overnight, is one of the most common complaints. [89], [27], [57]

Does desire change, or only the body?

This is the most striking pattern in the accounts. Many men describe hard, sometimes painful erections without any extra wanting, "robotic" or "just an erection". Many women describe feeling physically aroused, "everything woke up downstairs", while still not wanting sex. Others describe the reverse: a clear return of desire. [30], [29], [31], [150], [151]

This fits what the trials measured and did not: they asked about desire and distress with questionnaires, and satisfying sexual events did not increase. [22]

Does everyone respond?

No. Nonresponse is a recurring theme, more often among women, people past menopause and nasal-spray users. A 35-year-old woman prescribed a vial by her nurse practitioner got nausea most of the day and no effect. A woman on prescribed Vyleesi was "very bummed" to be a nonresponder, and another had a 36-hour headache. Some men used a whole vial up to 2 mg with nothing. [150], [152], [120]

When it does not work, people usually raise the dose, change the timing, add tadalafil or suspect the product. Community education groups add that hormones, medicines, relationship problems and other causes of low desire should be checked first. [55], [153]

What about nausea, flushing and feeling unwell the next day?

Nausea is the most common complaint, often in the first hour or two. Some people say it was mild; others were sick all day, or at every dose. Flushing, a red, hot face for an hour or more, is nearly as common. [144], [86], [32]

A next-day hangover is a frequent theme that the label does not describe: feeling "run down and achy", flu-like, drained or low for a day or two. Women taking Vyleesi describe restless legs, an urge to stretch, body aches, coughing and a stuffy nose; stretching and yawning were also recorded with Melanotan II in its first human study. [154], [155], [56], [156], [157]

What about erections that last too long?

Several men describe erections lasting 8–12 hours or into the next day, painful erections, or being worried enough about priapism to take action. One took 0.8 mg at bedtime and had erections all night strong enough to worry him; another described a recurring hours-long erection after 1.5–2 mg that he treated at home; one went to the emergency room after an 8-hour erection while also taking Cialis. [116], [115], [54], [158]

What about darker skin?

Darkening is reported mostly by people with darker skin or who used it often. One person whose face became two to three shades darker after three 1.75 mg doses over a few weeks said it had not reversed weeks after stopping; another "turned black for months". Others describe darker freckles and birthmarks, or new ones. [63], [64], [144], [159]

Does it stop working, or cause a crash?

Some people describe it working less well with repeated use, especially when doses are close together: a second 2 mg dose four days after the first did almost nothing for one man. Two long-term users describe becoming nonresponders who stayed that way after breaks of 6 and 8 months. [89], [151], [46]

Others describe a "crash" after an effective dose: "It's like it crams 2 weeks of libido into 24 hours," followed by up to two weeks of low desire. A few describe weeks of low desire or genital numbness after stopping. No study has measured tolerance or after-effects. [66], [65], [67], [160]

What do people using prescribed Vyleesi say?

In the 30 public WebMD reviews of Vyleesi we read, most were negative. The common complaints were severe nausea or vomiting even with ondansetron, restless legs, an urge to stretch, coughing and next-day tiredness; a smaller group described great results. Price is another theme: one woman said Vyleesi cost over $1,000 without insurance cover, so she bought a research vial instead. [56], [153], [161]

How can you judge a PT-141 story?

Useful questions: Was it prescribed Vyleesi or a research vial, and was the product tested? How much was taken, in micrograms, not "units" of an unknown mix? How long after the injection did the effect start? Was a Viagra-type drug, testosterone, a weight-loss drug or another peptide used at the same time? Was the person a woman before menopause, the group the trials studied? Did they post again after several uses? A single strong night proves little about safety, and skin changes take months to judge. [142], [60], [68]

How does PT-141 compare with Melanotan II, kisspeptin and oxytocin?

These peptides are sold side by side online for sex drive and are often combined. Status checked September 24, 2026.

The real differences are in evidence and approval. PT-141 is the only one of these approved for a sexual problem, and only for one narrow group; the others are either unapproved or approved for something else. It also differs from the other approved medicine for HSDD, flibanserin (Addyi), a tablet taken every day at bedtime rather than an injection before sex. No study has compared these peptides with each other, so the table cannot say which works better or is safer. [6], [5]

Common questions about PT-141

What is the FDA-approved PT-141 dose?

1.75 mg, injected subcutaneously with the Vyleesi autoinjector into the abdomen or thigh, at least 45 minutes before sex. No more than one dose in 24 hours, and more than eight doses a month is not recommended. The label says to stop after 8 weeks if there is no improvement, and there is no titration or cycle. [1] See typical protocols.

How long does PT-141 take to work?

The label says to inject at least 45 minutes before sex, and blood levels peak within about an hour. But the FDA noted that the best timing has not been worked out, and most people online describe the effect starting 2–12 hours after the injection and sometimes lasting into the next day. Many suggest testing it on a free day first. [1], [51], [30] See where protocols differ.

Is PT-141 approved for men? Does it work for erectile dysfunction?

It is not approved for men; the label says it is not indicated for HSDD in men or for enhancing sexual performance. Early studies found it could produce erections, including in some men who did not respond to Viagra, but they were small, and the largest has an expression of concern. Men online often describe erections without extra desire, and some describe erections lasting too long. [1], [28], [35], [29] See studies in men.

Can you take PT-141 with Viagra or Cialis?

The combination has barely been studied: one small trial used a nasal PT-141 dose with a low dose of sildenafil. Many people online combine injected PT-141 with tadalafil, and most reports of erections lasting too long, including an emergency-room visit, involve that combination. An erection lasting longer than 4 hours is a medical emergency. [75], [54], [20] See prolonged erections.

Is a 10 mg vial the same as Vyleesi?

No. The molecule may be the same, but Vyleesi is a sealed 1.75 mg dose made to medicine standards. A research vial's content, strength and sterility are not guaranteed, it has to be mixed and measured, and no stability study covers a mixed vial. The FDA has sent warning letters to sellers of research PT-141. [1], [21], [119] See storage.

Is PT-141 the same as Melanotan II?

No, although they are close relatives. PT-141 is the same ring of seven amino acids ending in an acid instead of an amide, and it was developed from Melanotan II to act on sexual function. Melanotan II is an unapproved tanning peptide; PT-141 is an approved drug with its own dose. Both can darken skin. [6], [3], [1] See the Melanotan II guide.

Does PT-141 make you sick? Does Zofran help?

Nausea is the most common side effect: 40% of women in the trials, mostly with the first dose. Taking 8 mg of ondansetron (Zofran) 30 minutes beforehand did not reduce nausea in a controlled study of 228 women, and the label does not recommend it as prevention. A doctor may prescribe anti-nausea medicine to take once nausea starts. [1], [19] See side effects.

Is it legal to buy PT-141?

Only as prescribed Vyleesi in the United States. Research PT-141 is unapproved there, and the FDA sent warning letters to five sellers in August 2026. In Canada, Health Canada has seized it as an unauthorized drug; in Australia, the regulator has argued it is prescription-only. [1], [119], [130], [133] See the dated legal-status summary.

Glossary

Plain explanations of the route, dosing, sexual-health and research terms used in this guide. Underlined terms in the text link here.

Adverse event

A harmful or unwanted medical event reported after someone used a treatment. A report alone does not prove the treatment caused it.

Ambulatory blood pressure monitoring

Wearing a cuff that measures blood pressure automatically throughout the day and night, to catch changes that a single clinic reading would miss.

Amino acid

A small chemical building block. Chains of amino acids make up peptides and proteins.

Anti-nausea medicine (antiemetic)

A medicine that prevents or relieves nausea and vomiting, such as ondansetron.

As needed (on demand)

Used only before a particular occasion, rather than on a fixed daily or weekly schedule.

Autoinjector

A prefilled, single-use pen that delivers a fixed dose into the skin at the press of a button. Vyleesi comes this way.

Bioavailability

How much of a dose reaches the bloodstream in a usable form. It depends heavily on the route.

Case report

A published description of what happened to one patient or a few. It can reveal a possible problem but cannot show how often it happens or prove the cause.

Compounding

When a pharmacy prepares a customized medicine from individual ingredients. In the US, federal lists control which bulk ingredients pharmacies may use.

Controlled trial

A study that compares people who receive a treatment with a similar group who do not, often receiving a placebo instead. Randomly assigning people to each group makes the comparison fairer.

Course and cycle

A course is the period of repeated use, such as six weeks. A cycle is a course plus a planned break before any further use.

Crossover study

A study in which each person receives both the treatment and the comparison, such as a placebo, on different occasions, so each acts as their own comparison.

Daily total

All the amounts given in one day, added together. For example, 250 mcg twice daily is a 500 mcg daily total.

Dose (amount each time)

The amount given on one occasion. A protocol lists both the dose and how often it is given.

Expression of concern

A notice a journal attaches to a published paper when there are serious questions about its reliability that have not been resolved. It is a warning, not a retraction.

Focal hyperpigmentation

Darkening of the skin in small patches rather than all over. With PT-141 it has appeared on the face, gums and breasts.

Female sexual arousal disorder (FSAD)

A lasting difficulty in becoming or staying physically aroused during sex that causes distress. It is related to, but different from, low desire.

Female Sexual Function Index (FSFI)

A questionnaire that scores desire, arousal, lubrication, orgasm, satisfaction and pain over the past four weeks. Its desire section runs from 1.2 to 6.

Freeze-dried (lyophilized)

Dried by freezing and removing the water, leaving a powder. Research PT-141 is sold this way and mixed with liquid before injection.

Half-life

The time it takes for the measured level of a substance in the blood to fall by half. It is not the same as how long an effect lasts.

Hypoactive sexual desire disorder (HSDD)

Persistently low sexual desire that causes a person distress and is not better explained by another condition, a medicine or relationship problems. Diagnosed by a clinician.

Hypothalamus

A small area at the base of the brain that helps control hormones, appetite, body temperature and sexual behavior.

Intranasal

Sprayed into the nose to be absorbed through its lining.

mcg and mg

Micrograms and milligrams. 1 mg equals 1,000 mcg. The approved PT-141 dose is 1.75 mg, or 1,750 mcg.

Melanocortin receptors (MC1R–MC5R)

A family of five sensors that respond to the body's melanocyte-stimulating hormones. MC1R on pigment cells controls skin color; MC3R and MC4R in the brain are linked to appetite and sexual function.

Open-label

A study in which everyone knows what they are taking, with no placebo. Results are more open to bias.

PDE5 inhibitor

A class of erection medicines, including sildenafil (Viagra) and tadalafil (Cialis), that widen blood vessels in the penis.

Peptide

A short chain of amino acids. PT-141 is a chain of seven, closed into a ring.

Placebo

A dummy treatment with no active ingredient, used as a comparison in studies.

Placebo response

Improvement in people given a dummy treatment, from expectations, extra attention or natural change over time. It is often large in studies that rely on how people feel.

Premenopausal

Before menopause, while a woman still has menstrual periods. Vyleesi is approved only for premenopausal women.

Priapism

An erection that lasts longer than four hours without sexual stimulation. It is a medical emergency that can permanently damage erectile tissue.

Reconstitution

Mixing a freeze-dried powder with a liquid so it can be measured and injected. The amount of liquid sets how much peptide each unit holds.

Research use only

A label on products sold for laboratory research. It does not mean a product is approved, tested for human use or legal to sell as a medicine.

Responder analysis

Counting how many people improved by at least a set amount, instead of comparing average scores. The threshold chosen affects the result.

Retraction

Withdrawal of a published paper by the journal, usually because its data or methods cannot be trusted. Its results should not be used.

Satisfying sexual events

A diary count of sexual experiences a person rated as satisfying. It was a secondary measure in the phase 3 trials and did not improve more than with placebo.

Schedule 4 (Australia)

Australia's prescription-only medicine category. Melanotan II and afamelanotide are listed by name; bremelanotide is not.

Shelf life

How long a product keeps enough of its strength to be used under stated storage conditions.

Subcutaneous (SC)

Injected into the fatty layer just under the skin. The Vyleesi autoinjector and research PT-141 injections both use this route.

Syringe units

Markings on an insulin syringe that measure volume. On a U-100 syringe, 100 units equal 1 mL. The amount of drug per unit depends on the vial's concentration.

Titration

Adjusting a dose in steps, usually starting lower and increasing if needed.

Troche

A small lozenge that dissolves between the cheek and gum or under the tongue. Compounded PT-141 troches have not been tested in people.

WADA

The World Anti-Doping Agency, which publishes the list of substances banned in sport.

Withdrawal and rebound

Withdrawal effects are symptoms caused by stopping a substance. A rebound is a problem returning worse than before after stopping. Neither has been studied for PT-141.

Explore more of the research

Go deeper into the animal, laboratory and early development studies behind the mechanism claims.

Across this guide, the citations include 34 original scientific papers: 7 cell, animal and laboratory papers, 24 human studies and case reports, and 3 laboratory analyses of product content and stability. The FDA's review also summarizes many company studies that were never published as papers; this guide cites those through the review, not as separate papers. Paper counts are not counts of independent research teams: most human studies were run or funded by the companies that developed PT-141.

In the route details, intraperitoneal means into the abdominal cavity; intravenous, into a vein.

How this guide was researched

This guide is built from a thorough review of the sources cited throughout it: published scientific studies, the approved medicine's label and the FDA's review of it, registered clinical-trial records, regulator warnings and published protocol descriptions. We also reviewed public online forums, public drug reviews and community education groups where people describe their own experiences with PT-141.

The guide cites 170 sources, including 34 original scientific papers. Each type of source answers a different question. Studies show what researchers measured. The label and regulators show what is approved, what is warned about and what must be monitored. Protocol descriptions show how PT-141 is typically used outside the label. Personal accounts show what individual people experienced. Every numbered citation links to its entry below, labeled by source type.

How this guide was made

Research and drafting were AI-assisted. Cited sources were checked against their originals, and each source entry notes when only an abstract or an indexed record was available. The guide was reviewed and edited by Doserly before publication. It has not had an independent clinical review, and Doserly does not currently have medical reviewers. Doserly makes a medication and health-tracking app and runs Doserly Academy, both of which are promoted in this guide. Read our editorial policy for how guides are researched, updated and corrected.

This guide is for educational purposes. It summarizes what the reviewed sources report so the research is easier to understand; it is not medical advice. For a deeper dive, or to check any point for yourself, go straight to the cited sources.

Explore the sources