PT-141, or bremelanotide, went through four clinical trials in men with erectile dysfunction before it reached a drug for women. In all of them it produced erections clearly more often than placebo. It also worked in men who did not respond to sildenafil, the active substance of Viagra. Below you will find how PT-141 differs from erection pills, what was measured in each of the four trials and what these results do not yet tell us.
How does PT-141 differ from sildenafil?
PT-141 acts in the brain, while sildenafil acts in the blood vessels of the penis. Sildenafil blocks the PDE5 enzyme, so the vessels widen more easily and blood flows in. On its own, however, it does not cause arousal. PT-141 stimulates melanocortin receptors, mainly MC1R and MC4R. Neurons with the MC4R receptor are found in many areas of the central nervous system.
This difference is clearly visible in the first trials. In healthy men PT-141 produced erections without any visual stimulation, that is without watching erotic material. Sildenafil does not work that way. That is why PT-141 is classed as a centrally acting drug and sildenafil as a peripherally acting one.
What did the four trials in men show?
The four trials covered several hundred people in total and tested two routes: nasal and subcutaneous. Three of them were run with Palatin Technologies, the company that developed PT-141. The table collects the key numbers.
| Trial | Who took part | Route and dose | Result |
|---|---|---|---|
| Diamond et al., 2004 | healthy men and patients who responded to Viagra | nasal, various doses | erections significantly more often than on placebo at doses above 7 mg, the first after about 30 minutes |
| Rosen et al., 2004 | healthy men and patients with a poor response to Viagra | subcutaneous, 0.3 to 10 mg | erections significantly more often than on placebo from doses above 1 mg, in patients at 4 and 6 mg |
| Diamond et al., 2005 | 19 patients who responded to Viagra or Levitra | 7.5 mg nasal together with 25 mg sildenafil | stronger response than sildenafil alone |
| Safarinejad and Hosseini, 2008 | 342 men who did not respond to sildenafil | 10 mg nasal before intercourse | good result in 33.5 percent against 8.5 percent on placebo |
How did PT-141 work when given nasally?
Given nasally, PT-141 produced an erection after about 30 minutes. The 2004 trial published in the International Journal of Impotence Research had two parts. The first involved healthy men, tested without visual stimulation. The second involved patients with erectile dysfunction in whom Viagra worked, tested with stimulation. Erections were measured with a RigiScan device, which records the circumference and rigidity of the penis.
In both parts erections occurred significantly more often than on placebo at doses above 7 mg. Blood levels rose with the dose and peaked after half an hour. The half-life was 1.85 to 2.09 hours. The most common side effects were facial flushing and nausea. The researchers did not find a dose that participants could not tolerate.
How did it work when given subcutaneously?
Given under the skin, PT-141 worked at lower doses than nasally. The second 2004 trial, in the same journal, tested doses from 0.3 to 10 mg in healthy men. Erections occurred significantly more often than on placebo at every dose above 1 mg. That threshold is several times lower than with the nasal route.
The second part of the trial involved patients for whom Viagra was not enough. A poor response meant that even a 100 mg dose gave an erection sufficient for intercourse in at most half of attempts. Patients received placebo and PT-141 at 4 mg and 6 mg in turn. Both doses gave significantly stronger erections than placebo. The authors concluded that PT-141 could be an alternative for people who do not respond to PDE5 inhibitors.
Can PT-141 be combined with sildenafil?
In the only trial of this combination, PT-141 with sildenafil gave a stronger erection than sildenafil alone. The paper was published in the journal Urology in 2005. It included 19 men who responded to Viagra or Levitra. Each went through three sessions in random order: 25 mg sildenafil with 7.5 mg PT-141 nasally, sildenafil alone and placebo alone.
Both doses were deliberately low, below typically effective ones. The combination gave a significantly stronger response than sildenafil alone at the same dose. No new side effects appeared, and known ones did not become more frequent. The authors saw this as an option for people who are harmed or not helped by higher doses of a single drug.
What about men who do not respond to sildenafil?
The largest trial included 342 men aged 28 to 59 in whom sildenafil did not work. It was published in the Journal of Urology in 2008. Participants used 10 mg PT-141 nasally or placebo at home, 45 minutes to two hours before intercourse. Each was to make at least 16 attempts. Results were assessed with the International Index of Erectile Function.
A good clinical result was achieved by 51 people, or 33.5 percent in the PT-141 group, against 13 people, or 8.5 percent on placebo. The PT-141 group also rated satisfaction with intercourse higher. Side effects were more frequent in this group. In 2023 the journal published an expression of concern about this paper, so we treat its figures as weaker than those of the other three trials.
Why was the drug approved only for women?
The approved bremelanotide drug, Vyleesi, received an indication in 2019 only for premenopausal women. It covers acquired low sexual desire that causes marked distress. The label states outright that the drug is not indicated in men or to improve sexual performance. Approval in men would require phase 3 trials in this group, and no such results have been published so far.
The Vyleesi label describes a dose of 1.75 mg under the skin, at least 45 minutes before intercourse. After each dose systolic blood pressure rises temporarily by up to 6 mmHg and diastolic by 3 mmHg. The peak falls between the second and fourth hour, and the heart rate slows by up to 5 beats per minute. Usually everything returns to baseline within 12 hours. In the approval trials nausea occurred in 40.0 percent of women and facial flushing in 20.3 percent.
Where to buy PT-141 and what is in the vial?
In the shop PT-141 is available in vials of 10 mg lyophilised powder from two brands. PT-141 10 mg Genheal costs 25 EUR. PT-141 10 mg Bio-Peptide costs 30 EUR. Both versions, a description of the molecule and prices per milligram are collected on the PT-141 page.
A 10 mg vial is a powder that has to be dissolved before use. How to do it step by step is described in the guide on how to reconstitute peptides. The related melanotan 2 has its own page, melanotan 2.
Where do these data end?
All four trials in men are short and date from 2004 to 2008. Three of them were run with the developer of the molecule, and the fourth carries an editorial expression of concern. None studied use over many months. PT-141 in the shop is material for laboratory research, not the drug Vyleesi, so it does not carry over its approval or its quality control. The status of such substances is described in the guide on the legal status of peptides.
Frequently asked questions
Does PT-141 work in men?
In four clinical trials from 2004 to 2008 PT-141 produced erections significantly more often than placebo, also in men with a poor response to Viagra.
How does PT-141 differ from Viagra?
PT-141 stimulates melanocortin receptors in the brain, while sildenafil widens the vessels of the penis. PT-141 produced erections even without visual stimulation.
How quickly does PT-141 work?
In the nasal trial the first erection appeared after about 30 minutes, and the blood level was highest after half an hour.
Can PT-141 be combined with sildenafil?
In a 2005 trial in 19 men, low doses of both substances together gave a stronger erection than sildenafil alone, with no new side effects.
Is PT-141 approved for men?
No. The drug Vyleesi from 2019 is indicated only for premenopausal women, and its label explicitly excludes men.
This is information about published research, not medical advice. The choice of treatment belongs to a doctor.
Sources
- Diamond LE, Earle DC, Rosen RC et al. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunction. International Journal of Impotence Research, 2004, 16(1): 51-59. https://doi.org/10.1038/sj.ijir.3901139
- Rosen RC, Diamond LE, Earle DC et al. Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra. International Journal of Impotence Research, 2004, 16(2): 135-142. https://doi.org/10.1038/sj.ijir.3901200
- Diamond LE, Earle DC, Garcia WD et al. Co-administration of low doses of intranasal PT-141, a melanocortin receptor agonist, and sildenafil to men with erectile dysfunction results in an enhanced erectile response. Urology, 2005, 65(4): 755-759. https://doi.org/10.1016/j.urology.2004.10.060
- Safarinejad MR, Hosseini SY. Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study. Journal of Urology, 2008, 179(3): 1066-1071. https://doi.org/10.1016/j.juro.2007.10.063
- FDA. Vyleesi (bremelanotide injection), prescribing information, 2019. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/210557s000lbl.pdf