Peptides for Sex: What the Research Shows in Men and Couples

Sexual Health & Intimacy Research

The peptides for sex with real human research behind them are PT-141 (bremelanotide), Melanotan II and oxytocin. PT-141 and Melanotan II act in the brain on melanocortin receptors rather than on blood flow, which is why studies measured both erections and desire. Oxytocin is the hormone released at orgasm. This article covers what each one did in human studies on erections, arousal and orgasm, how quickly the effects appeared, and the formats we supply.

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Findings

• In 20 men with erectile dysfunction, Melanotan II produced erections in 17, and increased sexual desire was reported after 68% of doses against 19% for placebo (P<0.01).
• Intranasal PT-141 produced erectile responses significantly greater than placebo in healthy men and in men with mild to moderate erectile dysfunction, with the first erection at about 30 minutes (2004).
• Given under the skin, PT-141 also produced significant erections in men who reported an inadequate response to Viagra (2004).
• In 19 men, low amounts of nasal PT-141 taken with low-strength sildenafil gave a stronger erectile response than sildenafil alone (2005).
• In 29 couples, intranasal oxytocin increased orgasm intensity and contentment after sex (2014).

How these peptides differ from ED tablets

Tablets such as sildenafil work in the penis: they block PDE5, an enzyme that ends an erection, so blood flow is sustained once arousal has started. They do not create desire.

PT-141 and Melanotan II work one step earlier, in the brain. Both are synthetic versions of alpha-melanocyte-stimulating hormone (alpha-MSH) and activate melanocortin receptors, chiefly MC3 and MC4, which sit in brain circuits that govern sexual motivation (Molinoff et al., 2003). That is why the studies below report two things at once: erections, sometimes without any sexual stimulation at all, and higher sexual desire.

Melanotan II came first, from the University of Arizona in the 1990s, where it was being studied for tanning. Volunteers reported spontaneous erections, which turned the research towards sexual function (Hadley, 2005). PT-141 was then developed from Melanotan II as a newer analogue, and it is the version that went on to large clinical trials.

What has Melanotan II research shown in men?

Study	Men	Result
Wessells, J Urol 1998	10, no organic cause	Erections in 8 of 10
Wessells, Urology 2000	10, organic risk factors	Erections after 12 of 19 doses vs 1 of 21
Wessells, IJIR 2000 (both groups)	20	Erections in 17; more desire 68% vs 19%

1998, psychogenic erectile dysfunction. In a double-blind, placebo-controlled crossover study, 10 men whose erectile dysfunction had no physical cause were monitored for six hours with a RigiScan device. Eight of the 10 developed clinically apparent erections on Melanotan II. Tip rigidity above 80% lasted a mean of 38.0 minutes on Melanotan II against 3.0 minutes on placebo (P=0.0045).

2000, organic risk factors. A second group of 10 men had physical risk factors for erectile dysfunction. Melanotan II initiated erections after 12 of 19 injections against 1 of 21 placebo doses, with a mean rigidity score of 6.9 out of 10 among responders and 45.3 minutes of tip rigidity above 80% against 1.9 for placebo. Sexual desire after injection was significantly higher than after placebo.

Both groups together. Across all 20 men, Melanotan II led to erections in 17 without sexual stimulation, and increased desire was reported after 13 of 19 doses (68%) against 4 of 21 placebo doses (19%). Nausea, yawning and stretching were the side effects most often recorded.

What has PT-141 research shown in men?

Nasal spray, 2004. PT-141 was given as a nasal spray to healthy men and to men with mild to moderate erectile dysfunction who responded to Viagra. In both studies, the erectile response at the higher amounts tested was statistically significant against placebo, and the first erection came at about 30 minutes. Blood levels peaked at a median of 0.5 hours with a half-life of about two hours. Flushing and nausea were the most common side effects, and no clinically significant changes appeared in vital signs, laboratory tests or ECGs (Diamond et al.).

Injection, men who did not respond well to Viagra, 2004. A companion study gave PT-141 under the skin to healthy men and to men who reported an erection suitable for intercourse no more than half the time on 100 mg Viagra. In the erectile dysfunction group, tested with visual sexual stimulation in a crossover design, the response was statistically significant at both amounts tested. The authors pointed to its ability to cause erections in men who do not respond adequately to a PDE5 inhibitor (Rosen et al.).

With sildenafil, 2005. Nineteen men with erectile dysfunction received low-strength sildenafil with nasal PT-141, sildenafil with a placebo spray, and placebo with placebo, in random order. The combination produced a significantly greater erectile response than sildenafil alone, and it did not add new side effects or make existing ones more frequent or severe (Diamond et al.).

PT-141 was ultimately developed for women, and in 2019 it was approved in the United States for low sexual desire in premenopausal women. The women’s research is covered in peptides for women’s libido.

Oxytocin and orgasm

Oxytocin is a nine-amino-acid hormone made in the hypothalamus. Two 1987 studies measured it during sex. In 9 men and 13 women, blood oxytocin rose during arousal and was significantly higher at orgasm than at baseline (Carmichael et al.). In 13 men, it rose from 1.4 to 7.3 pmol/L at ejaculation and returned to baseline within 30 minutes (Murphy et al.).

In 2014, a German team gave intranasal oxytocin to 29 healthy couples at home. Oxytocin increased the intensity of orgasm and contentment after intercourse, and these effects were stronger in men, who also reported greater sexual satiety. Women felt more relaxed, and some reported being better able to share sexual wishes with their partner. Drive and arousal measures were similar on oxytocin and placebo (Behnia et al.).

So oxytocin’s research sits at the other end of sex from PT-141: the orgasm, the afterglow and the bond, rather than the start of arousal. That pairing is the idea behind the Libido Spray Stack. The two are compared directly in PT-141 vs oxytocin.

How fast did the effects appear?

In the nasal PT-141 studies, the first erection came at about 30 minutes, and blood levels peaked at about half an hour. In the Melanotan II studies, erections were tracked over a six-hour window after injection. The oxytocin couples study gave the spray shortly before intimacy at home. These are study timings, recorded under trial conditions.

The formats we supply

• PT-141 10 mg vial and the ready-mixed PT-141 Nasal Spray in 10 mg and 20 mg, at about 350 mcg per spray.
• Melanotan II 10 mg vial and Melanotan II Nasal Spray.
• Oxytocin vial and Oxytocin Nasal Spray, about 70 mcg per spray.
• The Libido Spray Stack: PT-141 and oxytocin sprays together.

The sprays arrive pre-mixed with a metered pump. The vials are lyophilised powder and are reconstituted with bacteriostatic water; the steps are in how to reconstitute PT-141. For the full research area, see Sexual Health & Intimacy Research.

Frequently asked questions

What are the best peptides for sex?

The three with human research are PT-141, Melanotan II and oxytocin. PT-141 and Melanotan II act on melanocortin receptors in the brain and were studied for erections and desire. Oxytocin was studied for orgasm intensity and closeness after sex.

What has PT-141 research shown for erectile dysfunction?

In 2004 studies, nasal PT-141 produced erectile responses significantly greater than placebo, starting at about 30 minutes, and injected PT-141 produced significant erections in men who had an inadequate response to Viagra. In 2005, PT-141 with low-strength sildenafil outperformed sildenafil alone.

How is PT-141 different from Viagra?

Viagra (sildenafil) works on blood flow in the penis and needs arousal to start. PT-141 acts in the brain on melanocortin receptors, and studies recorded effects on both erections and sexual desire.

What did Melanotan II research show in men?

In 20 men with erectile dysfunction, Melanotan II produced erections in 17 without sexual stimulation, and increased desire was reported after 68% of doses against 19% for placebo.

Where can I buy PT-141 nasal spray in Canada?

Vistara Labs supplies PT-141 as a 10 mg vial and as a ready-mixed nasal spray in 10 mg and 20 mg, alongside Melanotan II and oxytocin, all shipped from within Canada by tracked Xpresspost.

References: Wessells H et al. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction. J Urol. 1998. PMID 9679884. Wessells H et al. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology. 2000. PMID 11018622. Wessells H et al. Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II. Int J Impot Res. 2000. PMID 11035391. Diamond LE et al. Intranasal PT-141 in healthy males and patients with mild-to-moderate erectile dysfunction. Int J Impot Res. 2004. PMID 14963471. Rosen RC et al. Subcutaneously administered PT-141 in healthy male subjects and in patients with an inadequate response to Viagra. Int J Impot Res. 2004. PMID 14999221. Diamond LE et al. Co-administration of low doses of intranasal PT-141 and sildenafil to men with erectile dysfunction. Urology. 2005. PMID 15833522. Molinoff PB et al. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003. PMID 12851303. Hadley ME. Discovery that a melanocortin regulates sexual functions in male and female humans. Peptides. 2005. PMID 15996790. Carmichael MS et al. Plasma oxytocin increases in the human sexual response. J Clin Endocrinol Metab. 1987. PMID 3782434. Murphy MR et al. Changes in oxytocin and vasopressin secretion during sexual activity in men. J Clin Endocrinol Metab. 1987. PMID 3654918. Behnia B et al. Differential effects of intranasal oxytocin on sexual experiences and partner interactions in couples. Horm Behav. 2014. PMID 24503174.

More on this: Peptides for Libido: What the Research Shows.