Myths about PT-141 (bremelanotide)

After FDA approval in 2019, bremelanotide (PT-141) became one of the most discussed "libido peptides." Advertising and forums present it now as "female Viagra," now as a safe alternative to any drugs for potency. The editorial team examined the most common claims and compared them with the results of clinical studies and the official label.

Myths about the mechanism of action

Myth 1: "PT-141 is female Viagra."The comparison with sildenafil sounds appealing but is misleading. Sildenafil and other phosphodiesterase-5 inhibitors act peripherally: they enhance the blood filling of the genitals once arousal has already arisen. Bremelanotide acts in the brain through melanocortin receptors, primarily MC4R, and affects sexual desire itself.

Interestingly, the name "female Viagra" was earlier given in the media to flibanserin — a completely different drug that is taken daily and acts on serotonin and dopamine mechanisms. Both agents have the same indication but entirely different pharmacology.

Myth 2: "Bremelanotide is the same as Melanotan II."Bremelanotide is indeed a metabolite of MT-II and differs from it only in the terminal group of the molecule. But it is precisely such small differences that affect the pharmacological profile. More importantly, bremelanotide went through a full clinical development program and obtained registration, whereas MT-II remained an experimental substance.

Myth 3: "It acts like a hormone and changes the hormonal background."Bremelanotide is not a sex hormone and does not replace estrogens or testosterone. It acts as a neuromodulator, affecting the brain's signaling pathways related to arousal and motivation.

Myths about efficacy

Myth 4: "PT-141 acts instantly and on everyone."In the phase 3 RECONNECT studies, bremelanotide statistically significantly improved desire measures and reduced the related distress compared with placebo (Kingsberg et al., 2019). However, the effect size was moderate, and some participants responded to treatment weakly. The label provides for discontinuation if there is no improvement after a few months.

Myth 5: "It is a universal aphrodisiac for men."Early studies of intranasal PT-141 in men with erectile dysfunction did indeed show enhancement of erection (Diamond et al., 2004). But that development program was halted, primarily due to an increase in blood pressure. The registered indication concerns only premenopausal women; efficacy and safety in men within the registered product have not been established.

Myth 6: "It will help with any decline in libido."The drug is approved for acquired generalized hypoactive sexual desire disorder — a diagnosis made after excluding other causes. If the decline in libido is related to depression, relationship problems, a side effect of medications, hormonal disorders or chronic fatigue, treatment should be directed at the cause.

Thus, bremelanotide is a tool for a clearly defined group of patients, not a "magic button" for libido.

Myths about safety

Myth 7: "A peptide means no side effects."The Vyleesi label lists significant adverse reactions. The most frequent is nausea, which in the phase 3 studies occurred in about 40% of participants, in some of pronounced intensity. Facial flushing, headache and injection-site reactions were also common.

Myth 8: "Blood pressure does not change."The label notes a transient increase in blood pressure and a decrease in heart rate after administration, which usually normalize within a day. That is precisely why the drug is contraindicated in uncontrolled hypertension and known cardiovascular disease.

Myth 9: "It can be used as much as you like."The official rules limit the number of administrations within a day and a month. One reason is focal hyperpigmentation of the skin of the face, gums and chest, which more often occurred with daily use and did not always resolve after discontinuation.

• Nausea, sometimes vomiting.
• Facial flushing, headache.
• Transient increase in blood pressure.
• Focal hyperpigmentation.
• Effect on the absorption of some oral drugs, in particular naltrexone.

Myths about "research" PT-141

Myth 10: "PT-141 from the internet is the same as pharmacy Vyleesi."The registered drug is manufactured to good manufacturing practice standards, has confirmed concentration, sterility and stability. Powders labeled "for research use only" have no such guarantees, and their actual composition may differ from what is stated.

Myth 11: "Since the drug is FDA-approved, it can be freely used by athletes and for any purpose."Approval concerns a specific indication and a specific product. Off-label use without a doctor deprives a person of medical oversight of contraindications and interactions. Athletes subject to doping control should check the status of any substance in the current WADA Prohibited List and with the national anti-doping agency.

Myth 12: "Illegal PT-141 is safer than Melanotan II."Even if the product really is bremelanotide, its action on MC1R can cause pigmentation, and on the cardiovascular system — an increase in blood pressure. And if the composition is unknown, comparing safety is impossible altogether.

That is precisely why the risk assessment for the "gray" market is substantially more complex than for a registered drug, for which there is a label and clinical trial data.

How to critically evaluate information

The first rule is to look for primary sources: the official FDA label and peer-reviewed publications of clinical trial results. They contain both efficacy data and a full list of adverse reactions and contraindications.

The second — distinguish human and animal studies, as well as the indications for which the drug was studied. Claims about the action of PT-141 in men or on athletes' "energy" have no evidence base within the registered product.

The third — pay attention to conflicts of interest. Sites that sell peptides have an interest in downplaying risks. Independent medical resources usually emphasize limitations and contraindications.

Finally, remember that a decline in libido is a common and quite treatable problem. A consultation with a gynecologist, urologist, endocrinologist or sexologist makes it possible to find the cause and choose an approach that will be effective specifically for you.

Editorial conclusions

Bremelanotide is not "female Viagra" and not a universal aphrodisiac. It is a centrally acting drug with a narrow indication and moderate efficacy in clinical studies.

The label describes real side effects — nausea, increased blood pressure, hyperpigmentation — and sets limits on the frequency of use and contraindications.

Products labeled "PT-141" sold outside pharmacies have nothing in common with the regulatory status of Vyleesi.

We also recommend our materials "The history of the discovery of PT-141 (bremelanotide)," "PT-141 (bremelanotide) and oncological risks: what studies say" and "Myths about Melanotan II."

References

1. Vyleesi (bremelanotide injection), for subcutaneous use. Prescribing information. U.S. Food and Drug Administration; 2019.
2. Kingsberg SA, Clayton AH, Portman D, et al. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019;134(5):899–908.
3. Clayton AH, Althof SE, Kingsberg S, et al. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Womens Health (Lond). 2016;12(3):325–337.
4. Diamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. 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. Int J Impot Res. 2004;16(1):51–59.
5. Dhillon S, Keam SJ. Bremelanotide: first approval. Drugs. 2019;79(14):1599–1606.
6. Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96–102.
7. World Anti-Doping Agency. The World Anti-Doping Code: International Standard — Prohibited List. Montreal: WADA; чинна редакція.