Low sex drive is one of the few goals in this field where a peptide has actually cleared a regulator. That peptide is bremelanotide, and knowing what its trials measured tells you what to expect from everything else on the list.
| Peptide | Tested in | What the trial measured | Status |
|---|---|---|---|
| PT-141 (bremelanotide) | 1,267 premenopausal women | Desire and distress scales | FDA-approved for HSDD |
| Kisspeptin | 32 women and 32 men with low desire | Brain responses; tumescence as secondary | 503A Category 2 |
| Oxytocin | 30 women, crossover | Sexual function index | Not established here |
| Melanotan II | 10 men with erectile dysfunction | Erections, with desire as secondary | On no compounding list |
The one with an approval
Two identical phase 3 trials, run together as RECONNECT, randomized 1,267 premenopausal women with hypoactive sexual desire disorder [1].
They injected 1.75 mg under the skin as needed, not on a schedule. Treatment ran 24 weeks, and the mean age was 39.
Desire scores rose by 0.35 points more than placebo across the two studies, and distress about low desire fell by 0.33 points more. Both results were significant at P<.001.
Those are small numbers on scales most people have never seen. They are also the largest, cleanest evidence any peptide has produced for this goal.
Tolerability is the trade-off. Nausea, flushing and headache each affected 10% or more of women in both trials.
The approval itself, and what the label covers, is set out in the PT-141 approval and trials. The male evidence is a separate and thinner story, in PT 141 for men.
Kisspeptin has trials, and they scan brains
Kisspeptin is the most interesting candidate here, and the easiest to overstate in either direction. It has been tested in people with low desire, twice, in randomized crossover trials.
The groundwork was in healthy men. In 29 of them, kisspeptin enhanced limbic activity in response to sexual and couple-bonding images compared with vehicle [2].
A second study found it enhanced brain responses to olfactory and visual cues of attraction [3]. The effect was largest in the men with the lowest sexual quality-of-life scores.
The first trial in patients randomized 40 premenopausal women with hypoactive sexual desire disorder, of whom 32 completed both visits [5]. Each visit was a 75-minute intravenous infusion or a rate-matched placebo.
Its outcome was brain activity, not a desire score. Kisspeptin modulated sexual and facial-attraction processing, and the size of that change tracked how distressed a woman was at baseline (r=0.469, P=.007).
The companion trial in men used the same design and added a physical measure [6]. Whole-brain modulation reached a Cohen d of 0.81 (95% CI 0.41 to 1.21, P=.003).
Penile tumescence in response to sexual stimuli rose by up to 56% more than placebo (P=.02), and self-rated happiness about sex rose by 0.63 points (P=.02). Kisspeptin was well tolerated in both trials.
So the signal is real and it is early. Both trials infused the peptide into a vein for 75 minutes inside a scanner, and neither ran long enough to measure whether anyone's sex life changed.
It also has no lawful route. Kisspeptin-10 sits in FDA's 503A Category 2, for substances that raise significant safety risks. More on it in the kisspeptin evidence.
The unapproved relative
Melanotan II is the compound bremelanotide was developed from, and it is widely sold for tanning and for arousal.
It was tested in people once, in 2000, and the result is why bremelanotide exists [7]. Ten men with erectile dysfunction received 0.025 mg per kilogram or vehicle, twice each, under blinded conditions.
Erections followed 12 of 19 active injections against 1 of 21 placebo doses. Rigidity above 80% lasted a mean 45.3 minutes versus 1.9 (P=0.047), and reported desire was significantly higher after the drug.
That trial is 26 years old, enrolled ten people, and measured erections with desire as a secondary note. Nothing larger has followed on desire.
The tolerability was the problem then and remains one. Four of the 19 injections caused severe nausea.
The other reason to be careful is what the compound does to skin. A 2025 case report describes oral mucosal malignant melanoma in a user of melanotan II nasal spray [8].
A single case cannot establish cause. It is still the kind of report that exists for this compound and does not exist for the approved one.
What to expect, honestly
A 2026 review of therapeutic peptides places bremelanotide among the approved agents with robust safety data, and the rest of this field among agents with limited clinical evidence [9].
That split is the practical takeaway. One option has been through trials and a label; the others have mechanisms and small studies.
Low desire also has causes a peptide does not touch, including medication effects, sleep, relationship context and mood. Those are worth ruling out first with a prescriber.
To compare prescribers for the approved option, see the PT-141 prescriber rankings, and for the rest of this goal, the sexual health hub.