Tests in people and animals · 02
How PT-141 works: brain activity changed, but desire gains were small
The developers sought help for lost desire by acting through the brain. Two Phase 3 studies found slight relief in women; other tests help explain the limits.
The clearest benefit was slight relief when women felt distressed by lost desire
The developers tested whether PT-141 could ease women's loss of desire through brain activity. In the larger tests, women reported a little more sexual interest and less bother about low desire. Only certain women who haven't reached menopause have approval for treatment of that lasting problem. If you're considering treatment for yourself, men's use isn't included in that approval.
PT-141 acts on receptors, the points where brain cells receive chemical messages. When those receptors become active, sexual messages can affect the brain differently. Erection pills mainly help the penis fill with blood, through a different action. Your wish for sex and your ability to get an erection aren't the same concern.
PT-141 brought erections in early tests of men and animals
Early PT-141 tests brought erections in men who couldn't readily get an erection [1]. The medicine also brought erections in rats and other primates, the animal group that includes monkeys and apes. Activity rose in the animals' brain cells, supporting an action that starts in the brain [1][2]. You can't infer a change in a man's desire from an erection alone.
The men's erections began soon after use, and the response increased as amounts rose. The cited summary doesn't give an exact waiting time or separate firmness from duration. These were early tests, rather than evidence that the treatment reliably fits your health. Findings in rats and the other animals add reasons for research, but don't establish human benefits.
A hormone is a chemical the body uses to carry messages between cells. The drug acts on two of five related kinds of receptors that receive those messages. The two kinds mainly help manage hunger and sexual interest through the brain. That explains the interest in desire, but your body's response can include more than sexual effects.
PT-141 hunger effects appeared, but hamsters showed no stronger sexual reward
The drug chiefly acts on receptor number 4, where brain cells receive hormone messages [1]. Receptor number 3 is affected less strongly, and these points also govern hunger. Frequent use changed eating and weight, without establishing sexual benefit or approved weight-loss care [6].
In 2025, researchers examined female Syrian hamsters' brain cells using dopamine, a message-carrying chemical [12]. They checked genes, which govern how cells make these message-receiving receptors. The drug didn't change those genes' activity in that brain area. That hamster result can't establish relief for you.
Researchers tested whether hamsters preferred an area where they had previously mated. After treatment, the hamsters showed no extra preference for the area where mating had occurred. That gave no evidence of more rewarding sex in those hamsters, without settling what you'd feel.
PT-141 benefits included less bother about low desire, with a small difference
Women receiving bremelanotide reported slightly increased sexual interest and less bother than women receiving placebo shots without medicine. In Phase 3 studies, women used 1.75 milligrams when needed, injected under skin, over 24 weeks [3]. Question 13 asked how bothered the women felt by their lack of desire. Both tests found gains in sexual interest and relief from distress, though the differences were small.
Chance alone was unlikely to account for the differences in the women's answers. Other researchers questioned whether those differences meant enough relief in day-to-day life. They've also questioned whether the questions used best measured benefits that people would value. You need both the slight improvement and those doubts when considering the findings.
A 2025 meeting report described improvements in women's physical arousal and orgasm, beyond their desire [14]. Another 2025 meeting report compared bremelanotide with flibanserin and testosterone treatment [15]. Flibanserin also treats distressing lost desire; the hormone testosterone helps govern sexual health. The comparison doesn't give enough detail here to tell you which treatment helped women most.
Meeting reports are shorter than full papers that other researchers have checked. The desire studies offer firmer findings than these brief reports about other benefits. None of the group results tells you that the medicine will suit your health. A doctor still needs to consider the possible relief alongside the unwanted effects.
Phase 3 studies found relief, while longer use often caused nausea
The Phase 3 studies, numbered 301 and 302, enrolled 1,267 women still before menopause. Women received 1.75 milligrams when needed through shots beneath the skin over 24 weeks [3]. The women and staff assessing them were both kept unaware of which shots contained medicine or placebo. Women receiving medicine felt slightly more sexual interest and less bother, but reported headache, nausea, and flushing, which means hot or red skin [3].
After the first 24 weeks, 684 women joined a 52-week follow-up while knowing they received medicine [4]. The desire gains continued, and no safety problems appeared beyond those already known. Nausea affected 40.4%; hot or red skin affected 20.6%; headache affected 12.0% [4]. These figures describe the women studied, rather than a forecast of your own side effects.
Feeling sick made the medicine hard to tolerate and caused some women to stop. Knowing they received the drug may also have affected how women described their benefits. The PT-141 side effects page gives more detail about that discomfort. You need to consider the small desire gain together with the chance of feeling sick.
MRI scans showed women’s brains reacting differently to sexual images
A study of 31 women before menopause found stronger desire lasting up to 24 hours [5]. All had troubling low desire and received medicine and placebo, shots without drug, at separate visits. The treatment order was kept unknown to both the women and the staff assessing them. MRI scans, which show activity inside the brain, found different reactions while women viewed sexual images.
Areas tied to feelings and awareness of the body worked together more strongly. Areas involved in movement also became more active during those tasks. The scans support the brain's involvement, beyond merely altering the amount of blood reaching sexual organs. Scans can't predict how much your desire would improve.
PT-141 FDA approval applies to certain women before menopause
FDA approved bremelanotide injection, first researched as PT-141, in June 2019 for a particular loss of desire [6][11]. The women covered haven't reached menopause, and their loss of sexual interest persists and causes distress. Previously, their desire was normal; the loss now affects more than one situation or partner. The approved instructions describe 1.75 milligrams when needed through an injection just below skin [6].
Men remain outside the approval, as do women past menopause and uses meant to improve sexual performance. Claims about those uses need their own evidence, despite approval for certain women. The approved instructions describe a different purpose from the early tests of men's erections. You can read PT-141 findings in men, but those tests haven't established approved treatment for you.