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The Peptide Effect
Comparison

PT-141 vs Melanotan II

PT-141 (bremelanotide, brand name Vyleesi) and Melanotan II are both melanocortin receptor agonists that enhance sexual arousal, but they differ significantly in selectivity and side-effect profile. PT-141 is a selective MC4R agonist developed specifically for sexual dysfunction and is FDA-approved for hypoactive sexual desire disorder (HSDD) in premenopausal women. Melanotan II is a non-selective melanocortin agonist that activates MC1R through MC5R, producing skin tanning, appetite suppression, and sexual arousal simultaneously — but remains an unapproved research chemical with a broader risk profile.

Side-by-side comparison diagram of PT-141 and Melanotan II mechanisms of action
Conceptual comparison — not to scale

Head-to-Head Comparison

CriteriaPT-141Melanotan II
Primary mechanismSelective MC4R agonist — central nervous system sexual arousal pathwayNon-selective MC1R–MC5R agonist — melanogenesis, sexual arousal, appetite regulation
FDA approval statusFDA-approved (Vyleesi) for HSDD in premenopausal women since 2019Not approved — unregulated research chemical
Primary use caseSexual dysfunction (low desire) in women; off-label for male EDSkin tanning; sexual enhancement is a secondary use
Route of administrationSubcutaneous injection (auto-injector for Vyleesi)Subcutaneous injection
Typical dosage1.75 mg subcutaneous, 45 min before activity (max 1 dose/24 hrs)0.25–0.5 mg subcutaneous daily during loading, then maintenance 1–2× weekly
Tanning effectNone — does not activate MC1R significantlyStrong — activates MC1R to stimulate melanogenesis (darkens skin without UV)
Appetite suppressionMinimal — MC4R activation may mildly reduce appetiteModerate — MC4R + MC3R activation reduces appetite noticeably
Onset of action~45 minutes after injection~1–2 hours for sexual effects; tanning develops over days to weeks
Duration of effect~6–12 hours for sexual arousal effects~4–8 hours for sexual effects; tanning is semi-permanent
Common side effectsNausea (40%), flushing, headache, injection site reactionsNausea, facial flushing, fatigue, darkening of moles/nevi, spontaneous erections
Safety concernsBlood pressure elevation (transient); not for use with cardiovascular conditionsUnregulated purity; mole darkening may mask melanoma detection; potential cardiovascular effects
Approximate cost$800–$1,000/month (Vyleesi); $50–$100/month (compounded)$30–$60/month (research chemical)

When to Choose Each

Choose PT-141

Female HSDD (FDA-approved), male sexual desire/arousal issues, targeted sexual enhancement without tanning

Choose Melanotan II

Sunless tanning with fair skin, combined tanning + sexual enhancement, appetite reduction as a side benefit

Verdict

PT-141 is the clear choice for targeted sexual dysfunction treatment — it is FDA-approved, has a well-characterized safety profile, and acts selectively on the MC4R pathway responsible for sexual arousal without the tanning and other off-target effects of Melanotan II. Choose Melanotan II only if skin tanning is your primary goal and sexual enhancement is a welcome secondary benefit, understanding that it carries greater safety uncertainty as an unregulated compound. For men specifically seeking erectile support, PT-141 can be effective but works through desire/arousal pathways rather than direct vascular mechanisms like PDE5 inhibitors.

References

  1. Bremelanotide for female hypoactive sexual desire disorder: the RECONNECT randomized trial (2019) — PubMed
  2. Melanocortin receptor agonists, penile erection, and sexual motivation (2005) — PubMed
  3. Melanotan II: a review of its clinical use and potential for misuse (2015) — PubMed
  4. FDA approval of bremelanotide (Vyleesi) for hypoactive sexual desire disorder (2020) — PubMed
  5. The melanocortin system and sexual function: a review (2009) — PubMed

Frequently Asked Questions

Does PT-141 work like Viagra?
No. PT-141 and Viagra (sildenafil) work through completely different mechanisms. Viagra is a PDE5 inhibitor that increases blood flow to the genitals — it is a vascular/mechanical effect. PT-141 acts on melanocortin-4 receptors in the brain to increase sexual desire and arousal at a central nervous system level. PT-141 affects desire and arousal, while Viagra primarily affects the physical ability to achieve erection. They can potentially be used together under medical supervision.
Is Melanotan II safe for tanning?
Melanotan II has not been evaluated by any regulatory agency for safety or efficacy. Key concerns include: darkening of existing moles, which can complicate skin cancer screening; unknown long-term melanoma risk; nausea and cardiovascular effects; and inconsistent purity from unregulated sources. Dermatologists generally advise against its use. The peptide is banned in Australia and several European countries.
Can men use PT-141 for erectile dysfunction?
PT-141 is FDA-approved only for premenopausal women with HSDD, but it is used off-label by men for sexual dysfunction. Clinical trials (Phase 3 for male ED were completed but not pursued for approval) showed efficacy for erectile dysfunction, particularly in men who did not respond to PDE5 inhibitors. It works through central arousal rather than vascular mechanisms, making it a different approach to ED treatment. Compounding pharmacies commonly formulate it for male use.
Was PT-141 actually derived from Melanotan II?
Yes. PT-141 (bremelanotide) was developed directly from Melanotan II research. When clinical investigators noticed that Melanotan II consistently caused sexual arousal as a side effect during tanning trials, they engineered PT-141 as a modified cyclic heptapeptide with greater selectivity for MC4R (the receptor responsible for sexual arousal) and reduced activity at MC1R (responsible for tanning). PT-141 is essentially a "refined" version of Melanotan II focused on sexual function.
Are PT-141 and Melanotan II legal to purchase?
PT-141 (bremelanotide) is FDA-approved as Vyleesi and available by prescription for premenopausal women with HSDD. Compounded PT-141 is also offered by some clinics for off-label use. Melanotan II has no regulatory approval in any major market and is banned for sale in several countries including Australia. In the US, it is sold as a research chemical not intended for human use. The legal landscape varies significantly by jurisdiction, and Melanotan II in particular carries additional safety concerns due to unregulated manufacturing. Consulting a healthcare provider about legal, regulated options is strongly recommended.

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