
Sexual desire in HSDD
In the RECONNECT trials, women taking bremelanotide had greater increases in sexual desire than placebo (an integrated difference of 0.35 points on the FSFI desire domain).1

Bremelanotide, Vyleesi
PT-141 descends from a peptide built to tan skin, and it ended up as an FDA-approved drug for low desire in premenopausal women. The approval is narrow, and the details matter.
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PT-141 is the research name for bremelanotide, sold as Vyleesi. It activates melanocortin receptors in the brain, a system tied to pigment, appetite and sexual response. FDA approved it in 2019 for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD). It is not indicated for postmenopausal women, for men, or to enhance sexual performance. Trial benefits were real and modest.
Medically reviewed by Robert Lufkin, MD (opens in a new tab)
Chief Medical Officer, Vitals Vault · Updated · 14 sources
It acts in the brain rather than on blood flow, and how it helps desire is not fully known.
Its targets sit mainly in the brain and spinal cord. In animals it switched on nerve cells in a deep brain region.1213
Erection pills act on blood vessels. In a 2006 study, women reported more desire with no clear difference in vaginal blood flow.135
The FDA label says how it improves low desire in women is unknown.13
The approved use rests on two phase 3 trials of 24 weeks. Results were statistically significant and modest, and one independent analysis questions the measures used.
This guide cites no findings at this level.
Shows a mechanism
In animals, PT-141 switched on nerve cells in the hypothalamus, a deep brain region.12
Shows an effect in a body
Two 24-week phase 3 trials in premenopausal women raised desire 0.35 points and cut distress 0.33 points vs placebo. The effects were modest.1
Shows it works in people
The full guide to PT-141
In the 1990s, a team at the University of Arizona was chasing a sunless tan. They had designed melanotan I and melanotan II, lab-made relatives of alpha-MSH, the hormone that tells pigment cells to darken the skin. The hope was a tan without the ultraviolet damage. Melanotan II went into a pilot safety study in Tucson, just three men, single-blind, alternating daily injections of drug and saline. In two of them it did darken the skin.
It also did something nobody had designed it for. The study recorded a stretching and yawning complex that seemed to arrive together with spontaneous erections, which came and went for one to five hours after a dose. Mild nausea appeared at most dose levels, an early preview of the side effect that would follow this family of molecules for decades.
By 1998 the Arizona group was testing melanotan II on purpose. In a placebo-controlled crossover study of 10 men with erectile dysfunction of no known organic cause, 8 developed clinically apparent erections. Nausea, yawning and a dip in appetite were the trade-offs, and none needed treatment.
PT-141 came next. Palatin Technologies developed it as a new analogue of melanotan II, and it later took the generic name bremelanotide. The tanning goal was left behind and sexual function became the target. Two decades on, it would become Vyleesi, an injection approved for one specific form of low desire in women.89107
The first human work with PT-141 itself was in men. In 2003, Palatin researchers reported that it produced erections in rats and monkeys, and that in healthy men and men with erectile dysfunction it caused a rapid, dose-dependent rise in erectile activity. A 2004 placebo-controlled study of a nasal form found erections began about 30 minutes after a dose, with flushing and nausea the most common complaints.
Then the work turned to women. In 2006, 18 premenopausal women with sexual arousal disorder took a single dose of bremelanotide and, at another visit, a placebo. More women reported moderate or high sexual desire after the drug. Yet a sensor measuring vaginal blood flow while they watched erotic videos detected no significant difference from placebo.
That mismatch is the interesting part. Desire moved and the blood-flow sensor did not, which is consistent with an effect that starts in the brain instead of the plumbing. The later phase 3 trials enrolled women with low desire, and the work in men did not lead to an approval.
Palatin ran the phase 3 trials, then licensed North American rights to AMAG Pharmaceuticals, which submitted the new drug application to FDA. Approval came in June 2019 for a self-administered injection used on demand.126571413
Most people know sexual medicine through erection pills, which act on blood vessels in the penis and need arousal to be under way already. PT-141 starts further upstream. Bremelanotide activates melanocortin receptors, a family of five that the body uses for jobs as different as skin pigment, appetite and sexual behavior.
Its label ranks potency as MC1R first, then MC4R, MC3R, MC5R and MC2R, and says binding at MC1R and MC4R is what matters at therapeutic levels. Neurons carrying MC4R are spread through many areas of the brain and spinal cord. In rats, PT-141 switched on neurons in the hypothalamus, in a region wired by nerve pathways to the penis.
The label is candid about the rest. It states that the mechanism by which Vyleesi improves HSDD in women is unknown. The receptors are known, and rat studies point to the hypothalamus, but the chain of events from receptor to a change in how much someone wants sex has not been mapped.
The timing is short. After an injection, bremelanotide has a half-life of about 2.7 hours, and the label notes that how long the effect lasts after each dose has not been established. It is used as needed before anticipated sexual activity, so it acts as an occasional nudge to a brain circuit and is never meant to build up in the body.13125
The approval rests on two identical phase 3 trials, studies 301 and 302, known together as RECONNECT. Between 2015 and 2016 they randomized 1,267 premenopausal women with HSDD to bremelanotide or placebo for 24 weeks. The women averaged 39 years of age, 96.6 percent were enrolled at US sites, and 85.6 percent were white.
Two outcomes were chosen in advance. One was the desire domain of the Female Sexual Function Index, a questionnaire. The other was a single item asking how much low desire distressed the woman. Across both trials combined, bremelanotide raised the desire score by 0.35 points more than placebo and lowered distress by 0.33 points more. Both differences were statistically significant.
A measure that did not move tells you as much. The label reports no significant difference between bremelanotide and placebo in the change in satisfying sexual events, a secondary endpoint. Put plainly, women on the drug reported wanting sex more and minding their low desire less, without a measurable rise in how often they had satisfying sex.
Women who finished the core trials could continue in a 52-week open-label extension. Of 856 eligible women, 684 joined and 272 completed it. No new safety signals appeared, and improvements were sustained among those who stayed, a group that by design includes only women who chose to keep going.1213
In a paper published online in 2023, two psychologists at Metropolitan State University in Minnesota went back to the RECONNECT data and asked whether the questionnaires used actually measure HSDD well in women. They concluded that the desire domain and the distress item have questionable validity evidence for this group, and that the published responder categories had none.
They also found that 8 of the 11 efficacy outcomes registered on ClinicalTrials.gov had never been published, including total scores for both questionnaires. When they analyzed those, effect sizes ranged from nil to small. Their summary was that bremelanotide’s benefits are statistically modest and limited to outcomes with scant validity evidence in women with HSDD.
Neither reading cancels the other. The phase 3 trials were large, placebo-controlled and positive on their prespecified endpoints, which is why FDA approved the drug. The reanalysis is a reminder that a statistically clear result can still be a small one for any individual woman. The label builds that in, telling prescribers to stop after 8 weeks if she does not report an improvement.4113
Remember where PT-141 came from. Its parent molecule was built to darken skin, and MC1R, the receptor bremelanotide activates most potently, is the main switch on the pigment cells that make melanin. The program moved from tanning to desire, but the molecule kept its first talent.
It shows up in the safety data. In the phase 3 trials, 1 percent of women using it within the label’s limits developed focal hyperpigmentation, patches of darker skin on the face, gums or breasts. In a separate study where it was given every day for eight days, 38 percent did, and the label notes that the darkening did not clear in some women.
That gives a practical rule. Pigment risk climbs with frequency and is higher in darker skin, so the occasional, as-needed pattern the drug was approved for is also the pattern that keeps this side effect rare. Daily use is what raised it most in studies, which is one more reason a self-made schedule is a poor idea.
Linking the dark patches to MC1R is our reading of the label’s receptor data, a hypothesis the trials did not test directly. It fits the family history, though. The receptor that made melanotan a tanning candidate is the one bremelanotide hits hardest, and nausea, the other side effect noted in the first melanotan volunteers, has stayed with the family too.13893
Nausea is the most common side effect. In the integrated phase 3 data, 40.0 percent of women on bremelanotide reported nausea, against 1.3 percent on placebo. The label says 13 percent needed anti-nausea medicine and 8 percent stopped because of it, and that nausea improved for most women with the second dose.
Flushing came next at 20.3 percent, then headache at 11.3 percent and injection site reactions at 5.4 percent. Across the whole development program, 3,500 people took part in 43 completed studies, with no deaths and a few serious adverse events. Most side effects were mild to moderate.
Blood pressure deserves a careful look. After each dose, bremelanotide briefly raises blood pressure, by up to 6 mmHg systolic and 3 mmHg diastolic at the peak two to four hours later, and lowers heart rate by up to 5 beats per minute. Both usually return to baseline within 12 hours. The label contraindicates it in uncontrolled high blood pressure and known cardiovascular disease.
Two interactions matter. Bremelanotide can slow stomach emptying and change how oral medicines are absorbed, and it can sharply lower blood levels of oral naltrexone, so the label says to avoid it with naltrexone products used for alcohol or opioid addiction. It also advises stopping if pregnancy is suspected and using effective contraception while taking it.313
Because the story began with erections, many men ask whether PT-141 is for them. The early human data were in men. PT-141 produced rapid, dose-dependent erectile responses in healthy men and in men with erectile dysfunction, and in a placebo-controlled study erections began about 30 minutes after a nasal dose.
Those were small, early-phase studies, and they did not lead to an approved product for men. The Vyleesi label is explicit on three counts. It is not indicated for HSDD in men, it is not indicated for HSDD in postmenopausal women, and it is not indicated to enhance sexual performance in anyone.
That leaves men in a gray zone. The side-effect numbers above, especially nausea and the blood pressure rise, were measured in premenopausal women using the approved product, so they cannot simply be carried over. A vial labeled PT-141 and sold online is a different thing again, with no assurance of what is inside it.
Researchers are exploring other routes into the brain’s desire circuitry for men. In a 2023 randomized trial of men with HSDD, a single infusion of kisspeptin, a reproductive hormone, changed activity in the brain’s sexual-processing network and increased penile responses to erotic videos compared with placebo. It is early work, and a separate story.1261311
HSDD is a diagnosis of exclusion. The label’s definition requires that low desire is not due to a co-existing medical or psychiatric condition, problems with the relationship, or the effects of a medication. A clinician works through that with your history, medicines and an examination, and blood work fills in the parts a conversation cannot, such as a high prolactin or an underactive thyroid. No blood test diagnoses HSDD.
Estradiol and total testosterone describe the sex hormone background. Both shift across the menstrual cycle and with hormonal contraception, so a clinician reads them in context instead of against a single cutoff. Testosterone contributes to desire in women as well as men, but no testosterone level diagnoses HSDD, so a clinician decides whether checking it answers a real question for you.
Prolactin is the easy one to miss. A raised level, from a small pituitary growth or from some medicines, can lower desire and gives few other clues without a test. TSH screens the thyroid, since an underactive thyroid can sap energy and libido in ways that look a lot like low desire.
This is how Vitals Vault approaches it. A blood panel at Quest Diagnostics comes first, a licensed clinician reviews the results with your history, medicines and blood pressure, and any prescription decision comes after the reversible causes have been looked for.13
FDA approved bremelanotide as Vyleesi under NDA 210557 on June 21, 2019. The indication is the treatment of premenopausal women with acquired, generalized hypoactive sexual desire disorder, characterized by low sexual desire that causes marked distress or interpersonal difficulty and is not due to a co-existing medical or psychiatric condition, problems with the relationship, or the effects of a medication or drug substance.
Acquired means the low desire developed in someone who previously had no problems with desire. Generalized means it happens regardless of the type of stimulation, situation or partner. The label then sets limits of use. Vyleesi is not indicated for HSDD in postmenopausal women or in men, and it is not indicated to enhance sexual performance.
The approval belongs to a specific product, a prefilled autoinjector, tested in the trials described here. Products sold online under the name PT-141 are not that product and were not part of the approval.1413
PT-141 is one of the few peptides with a full drug-approval story behind it: a tanning experiment, a surprise in the side-effect notes, a pivot from men to women, and two large trials that showed a real but modest lift in desire and a drop in distress. It works in the brain, its side effects are predictable, and its skin effects still recall where it came from.
If you are a premenopausal woman whose desire has faded and it bothers you, the first question is what changed. Hormones, thyroid, prolactin, medicines, sleep, mood and the relationship all come before a prescription. If those check out, the next question worth asking your clinician is how the two of you will judge, at 8 weeks, whether it is working.1413
A prescription starts with a clinician confirming HSDD and ruling out other causes, from hormones and thyroid to medicines and mood. Vyleesi is injected as needed before anticipated sexual activity, and the label notes that how long each dose keeps working has not been established. Nausea is most common after the first injection and improved for most women with the second.
Benefit, when it comes, is judged over weeks. RECONNECT measured change over 24 weeks, and the label tells prescribers to stop after 8 weeks if a woman does not report an improvement. Knowing that checkpoint in advance makes the trial a fair test for both of you.131
Dorr et al., 19969
Pilot phase I study · Volunteers given melanotan II, the parent molecule
Darkened skin in some; spontaneous erections and mild nausea also recorded
Limits: Three men, single-blind, and a different molecule
Wessells et al., 199810
Placebo-controlled crossover · 10 men with erectile dysfunction of no known organic cause
8 of 10 had erections on melanotan II
Limits: Melanotan II, not PT-141; very small
Diamond et al., 20046
Placebo-controlled trials of a nasal form · Healthy men and men with erectile dysfunction
Erections began about 30 minutes after a dose; flushing and nausea most common
Limits: Early phase; did not lead to approval for men
Diamond et al., 20065
Placebo-controlled crossover, single dose · 18 premenopausal women with sexual arousal disorder
More reported moderate or high desire; no significant difference in vaginal blood flow versus placebo
Limits: Small, one dose, different diagnosis from the approval
Kingsberg et al., 2019 (RECONNECT)113
Two phase 3 randomized trials, 24 weeks · 1,267 premenopausal women with HSDD
Desire up 0.35 points and distress down 0.33 points versus placebo
Limits: Modest effects; no difference in satisfying sexual events
Simon et al., 20192
52-week open-label extension · 684 women entered, 272 completed
No new safety signals; improvements sustained in those who continued
Limits: No placebo group; heavy dropout
Clayton et al., 20223
Safety review of the full program · 3,500 people in 43 completed studies
Nausea 40.0% vs 1.3%; brief blood pressure rise; rare skin darkening at label use
Limits: Authors linked to the developers
Spielmans and Ellefson, 20244
Independent reanalysis · RECONNECT trial data
Benefits statistically modest; outcome measures have scant validity evidence
Limits: Reanalysis, not a new trial
It works differently. Erection pills act on blood vessels, while bremelanotide activates melanocortin receptors in the brain. In a 2006 study, women reported more desire, with no significant difference from placebo in vaginal blood flow. The label says its exact mechanism in HSDD is unknown.135
The approval covers premenopausal women with acquired, generalized HSDD only. The label states it is not indicated for postmenopausal women, for men, or to enhance sexual performance.13
They are related but different. PT-141 was developed as a new analogue of melanotan II, which was designed for tanning. Bremelanotide went through phase 3 trials and FDA approval; melanotan II did not.814
Not in the trials. Women on bremelanotide reported more desire and less distress, but the label reports no significant difference from placebo in the number of satisfying sexual events.113
Vyleesi is a prefilled autoinjector given under the skin of the abdomen or thigh as needed before anticipated sexual activity, with limits on how often it can be used. The label sets the details and a prescriber decides.13
For Vyleesi, the FDA label sets one injection under the skin of the belly or thigh, used as needed at least 45 minutes before sex, no more than once in 24 hours, and no more than eight doses a month, stopped after eight weeks if there is no improvement. There is no approved dose for men or any other use. Your clinician sets your dose.13
Vyleesi is labelled as one prefilled autoinjector dose under the skin of the abdomen or thigh, used only as needed before sexual activity, with firm limits on how often. A nasal spray was tested in men in early trials but was never approved. A prescriber decides whether the labelled dose fits you.
Already have a prescribed dose? The peptide dosage calculator turns it into the units to draw on an insulin syringe.
FDA label · Injection under the skin of the abdomen or thigh (autoinjector)
1.75 mg
As needed, at least 45 minutes before anticipated sexual activity; no more than 1 dose in 24 hours; more than 8 doses per month not recommended13
Premenopausal women with acquired, generalized HSDD. Stop after 8 weeks if symptoms do not improve.
Human trial · Nasal spray (investigational, never approved)
Single doses tested; erections above placebo at doses greater than 7 mg
Single dose per study session6
Healthy men and men with mild-to-moderate erectile dysfunction who responded to sildenafil (Viagra). No maximum tolerated dose was identified.
A clinician makes the call. These are the questions they will ask first.
Vitals Vault peptide care starts with a blood panel and a licensed clinician, and ends with a retest.
Get early access to peptide care| Attribute | PT-141 | Melanotan II |
|---|---|---|
| Molecule | Bremelanotide, a single defined peptide | Melanotan II, a different peptide |
| FDA status | Approved as Vyleesi for one use | Not approved, on FDA’s safety-risk list |
| Studied for | Low desire in women, erectile function in men | Tanning and erectile function |
Sexual desire is not a single switch. HSDD is diagnosed only after other causes are considered, and the Vyleesi label excludes low desire explained by another medical or psychiatric condition, relationship problems or a medication.
So a clinician starts by looking for contributors that can be corrected, including thyroid, sex hormone, prolactin and medicine effects, before a prescription is considered.13
A blood test before you start and a retest after shows what actually changed for you. It is how Vitals Vault approaches every treatment.
Yes, for one use. FDA approved bremelanotide, sold as Vyleesi, in June 2019 for the treatment of premenopausal women with acquired, generalized hypoactive sexual desire disorder, as characterized by low sexual desire that causes marked distress or interpersonal difficulty and is not due to a co-existing medical or psychiatric condition, problems with the relationship, or the effects of a medication or drug substance. Its label states it is not indicated for postmenopausal women or men, or to enhance sexual performance.1314
2003
Early work describes PT-141 as a melanocortin agonist producing erectile activity in men.12
2006
Small trial in premenopausal women with sexual arousal disorder reports more moderate or high desire after bremelanotide.5
June 2019
FDA approves bremelanotide as Vyleesi for premenopausal women with acquired, generalized HSDD.14
November 2019
The RECONNECT phase 3 trials and their 52-week extension are published in Obstetrics and Gynecology.12

PT-141 is bremelanotide, sold as Vyleesi. FDA approved it for premenopausal women with acquired, generalized hypoactive sexual desire disorder. It was also studied in men with erectile dysfunction, which is not an approved use.
In two phase 3 trials, women with HSDD reported greater increases in sexual desire and less distress than on placebo. The differences were statistically significant and modest.
It activates melanocortin receptors, mainly MC1R and MC4R at therapeutic levels, with MC4R neurons found across the brain. FDA says the exact mechanism for improving HSDD is unknown.
The most common are nausea (40% in trials), flushing, injection site reactions, headache and vomiting. It can briefly raise blood pressure, and about 1% had focal skin darkening.
Vyleesi is not indicated for men. Small early studies explored it for erectile dysfunction in men, but no approval followed. Talk with a clinician, and avoid products of unknown content sold online.
They are related but different peptides. PT-141 was developed as a new analogue of melanotan II, a tanning candidate. PT-141 (bremelanotide) is FDA-approved as Vyleesi for one use. Melanotan II is not approved and appears on FDA’s list of compounding substances with significant safety risks.
For Vyleesi, the FDA label sets one injection under the skin, as needed at least 45 minutes before sex, no more than once in 24 hours and no more than eight times a month. There is no approved dose for men or other uses. Your clinician sets your dose.
Yes, as bremelanotide (Vyleesi), since June 2019, for premenopausal women with acquired, generalized HSDD. It is not approved for men, postmenopausal women or to enhance sexual performance.
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