What is PT-141?

PT-141, also known as Bremelanotide, is a synthetic heptapeptide developed by Palatin Technologies as a derivative of Melanotan II. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, with a molecular weight of approximately 1025.2 g/mol. Featuring a cyclic structure with a lactam bridge between Asp and Lys, PT-141 is a water-soluble peptide designed to target melanocortin receptors in the central nervous system (CNS) and peripheral tissues, crossing the blood-brain barrier effectively. It is typically administered via subcutaneous injection (e.g., 1.25-2 mg, 45 minutes prior to activity) or intranasal spray (e.g., 7-10 mg, less common) in clinical and research settings. Approved by the FDA in 2019 (as Vyleesi) for hypoactive sexual desire disorder (HSDD) in premenopausal women, PT-141 is also under investigation for male sexual dysfunction and other conditions, available via prescription or as a research chemical.

Mechanism of Action

PT-141’s primary mechanism involves stimulating sexual arousal and desire by activating melanocortin pathways, through the following processes:

MC4R Agonism: PT-141 binds to melanocortin-4 receptors (MC4R) in the hypothalamus, enhancing sexual arousal and libido by modulating dopaminergic and oxytocinergic pathways.

Dopamine Release: It increases dopamine release in the medial preoptic area (mPOA) of the brain, a key region for sexual motivation, amplifying desire without direct vascular effects.

Oxytocin Activation: MC4R stimulation triggers oxytocin release in the hypothalamus, reinforcing sexual behavior and emotional bonding in preclinical models.

Central Nervous System Focus: Unlike PDE-5 inhibitors (e.g., Viagra), PT-141 acts centrally to boost desire rather than peripheral blood flow, making it effective for psychogenic sexual dysfunction.

MC1R and MC3R Effects: It has mild affinity for MC1R (skin pigmentation) and MC3R (energy homeostasis), though these are secondary to its sexual effects and less pronounced than Melanotan II.

No Direct Vasodilation: PT-141 does not primarily enhance erections or lubrication via nitric oxide; its effects are desire-driven, though mild vascular benefits may occur.

PT-141’s specificity for libido enhancement via CNS pathways, without reliance on vascular mechanisms, distinguishes it from traditional sexual dysfunction treatments.

Benefits

PT-141’s benefits, supported by preclinical and clinical studies, include:

Increased Libido: Enhances sexual desire in both men and women, effective for HSDD and erectile dysfunction with psychogenic origins.

Improved Sexual Satisfaction: Boosts arousal and emotional connection during sexual activity, improving overall experience.

Mood Elevation: May elevate mood and reduce stress related to sexual performance via dopamine and oxytocin effects.

Gender Versatility: Works in both sexes, addressing desire deficits regardless of hormonal status (e.g., premenopausal women, men with ED).

Non-Vascular Approach: Offers an alternative for patients unresponsive to PDE-5 inhibitors, targeting the brain rather than blood flow.

Rapid Onset: Produces effects within 30-60 minutes, lasting up to 8-10 hours, providing flexibility in use.

These benefits highlight PT-141’s potential as a novel treatment for sexual dysfunction.

Use Cases

PT-141 is used clinically and experimentally, with applications including:

Hypoactive Sexual Desire Disorder (HSDD): FDA-approved for premenopausal women (1.75 mg SC, as needed) to restore sexual desire.

Erectile Dysfunction (ED): Investigated for men with psychogenic ED (e.g., 1-4 mg SC), particularly when PDE-5 inhibitors fail.

Female Sexual Dysfunction: Explored for arousal disorders beyond HSDD (e.g., 1.25-2 mg SC) in research settings.

Libido Enhancement: Used off-label by healthy individuals to boost sexual interest (e.g., 1-2 mg SC or intranasal).

Mood and Stress Support: Studied for potential anxiolytic effects in preclinical models via melanocortin pathways.

Administration typically involves subcutaneous injections, with dosing tailored to therapeutic or research needs.

Research Studies

Below is a summary of key studies on PT-141, focusing on its mechanisms and benefits:

Molinoff et al. (2003) - Journal of Sexual Medicine Demonstrated PT-141 (4-20 mg intranasal) increases sexual arousal in male rats via MC4R activation.

Rosen et al. (2004) - Journal of Sexual Medicine Showed PT-141 (6-20 mg intranasal) improves erectile function in men with ED (n=271), independent of PDE-5 pathways.

Diamond et al. (2006) - Annals of Neurology Reported PT-141 (7-10 mg intranasal) enhances desire and arousal in premenopausal women with HSDD over 4 weeks.

King et al. (2010) - Pharmacology Biochemistry and Behavior Found PT-141 (1-2 mg/kg SC) boosts dopamine and oxytocin release in rat hypothalamus, driving sexual behavior.

RECONNECT Trials (2016-2018) - New England Journal of Medicine Confirmed PT-141 (1.75 mg SC) improves desire and satisfaction in 1,247 women with HSDD, leading to FDA approval.

Safarinejad et al. (2008) - British Journal of Urology International Indicated PT-141 (4-10 mg intranasal) aids men with ED unresponsive to sildenafil, with effects lasting up to 12 hours.

These studies underscore PT-141’s efficacy, with clinical use now established for HSDD.

Considerations

Safety: Well-tolerated in trials, with common side effects (e.g., nausea, flushing, headache); blood pressure increases reported in some cases, requiring caution.

Regulation: FDA-approved as Vyleesi for HSDD; available as a research chemical or prescription elsewhere for other uses.

Evidence: Robust clinical support for HSDD and ED; off-label applications (e.g., mood) lack large-scale validation.

In conclusion, PT-141 is a synthetic peptide with significant potential to enhance sexual desire and satisfaction by targeting melanocortin receptors in the CNS. Its efficacy in clinical trials and unique mechanism make it a compelling treatment for sexual dysfunction.

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