Educational reference, not medical advice. This page summarizes information from published research and regulatory filings for educational purposes. It is not a recommendation to use any compound and should not replace guidance from a licensed healthcare provider. Most peptides discussed here are not approved for the uses described.
What it is
PT-141 — generic name bremelanotide, brand name Vyleesi — is a synthetic cyclic seven-amino-acid peptide derived from alpha-melanocyte-stimulating hormone (alpha-MSH). It is structurally close to melanotan II, with one key difference: PT-141 carries a carboxyl group where melanotan II carries an amide. That single change shifts the activity profile away from skin pigmentation and toward central nervous system effects on sexual arousal.
Unlike most peptides in this library, PT-141 is an approved drug. It was developed by Palatin Technologies and approved by the FDA in June 2019 as Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women.
History
The compound traces back to the melanotan research program at the University of Arizona in the 1980s and early 1990s, where investigators developing alpha-MSH analogs for sunless tanning observed that some compounds also produced sexual arousal in male volunteers. Palatin Technologies licensed and refined the chemistry through the 1990s and 2000s, ultimately separating the tanning activity from the sexual-arousal activity by changing the C-terminal group.
Diamond and colleagues published the first formal sexual-arousal trial in premenopausal women in 2006. The pivotal RECONNECT program (two randomized Phase 3 trials totaling roughly 1,200 women) read out in 2017 and supported the 2019 FDA approval. PT-141 was also studied for erectile dysfunction in men but the development for that indication did not advance.
Regulatory status
FDA approved June 21, 2019 as Vyleesi for premenopausal women with acquired, generalized HSDD — defined as low sexual desire that causes marked distress or interpersonal difficulty and is not attributable to a coexisting medical or psychiatric condition, problems within the relationship, or the effects of a medication or other drug substance. The label specifically excludes postmenopausal women and men, reflecting the populations studied in the registration trials.
Not approved by the EMA. Approved in some other jurisdictions through bilateral filings. Compounded bremelanotide is sold extensively in the United States outside the approved Vyleesi product, often labeled "PT-141" — these are distinct from the FDA-approved drug and not produced under the same quality system.
Mechanism
Bremelanotide is a non-selective agonist of the melanocortin receptors with primary central activity at MC4 and secondary activity at MC1, MC3, and MC5. The mechanism for the sexual desire indication is believed to be central — activation of MC4 receptors in the hypothalamus and related limbic circuits modulates sexual motivation independently of vascular or hormonal pathways. This distinguishes it from the PDE5 inhibitors (sildenafil, tadalafil), which act on peripheral vasculature.
The MC1 activity is responsible for the transient hyperpigmentation and darkening of moles reported in trials. The MC4 activity is responsible for the central effects on appetite and nausea that are the most common dose-limiting side effects.
Half-life and dosing intervals
Published terminal half-life of subcutaneous bremelanotide is approximately 2.7 hours (range 1.9 to 4.0 hours). It is dosed on-demand rather than continuously: a single subcutaneous injection at least 45 minutes before anticipated sexual activity, with a maximum of one dose per 24 hours and no more than eight doses per month per the Vyleesi label.
The approved Vyleesi dose is 1.75 mg per subcutaneous injection delivered by a pre-filled autoinjector. Compounded PT-141 sold outside the label is typically available in higher-concentration vials (commonly 10 mg) intended to be drawn in smaller volumes; the dose-response above 1.75 mg has not been formally characterized in the published trials.
Reconstitution example
The approved Vyleesi product ships in a pre-filled autoinjector and does not require reconstitution. Compounded PT-141 is typically supplied lyophilized in 10 mg vials. A 10 mg vial reconstituted with 2 mL of bacteriostatic water yields 5 mg/mL. On a 1 mL U-100 insulin syringe, 35 units (0.35 mL) delivers approximately 1.75 mg — the labeled dose. Vial's calculator handles the conversion when vial mass and water volume are entered.
What to know
- Approved for a narrow indication. Vyleesi is approved for premenopausal women with HSDD. Other uses — male sexual dysfunction, postmenopausal women, recreational arousal — are off-label and not supported by the registration trials.
- Common reported side effects in RECONNECT: nausea (40%), flushing, injection-site reactions, headache. Nausea was the most frequent reason for discontinuation.
- Blood pressure effect. Bremelanotide produces a transient rise in blood pressure (approximately 6 mmHg systolic) lasting several hours post-dose. The Vyleesi label cautions against use in uncontrolled hypertension or known cardiovascular disease.
- Hyperpigmentation. Focal hyperpigmentation of the face, gums, and breasts, and darkening of existing moles, was reported in roughly 1% of women in trials. The change may not fully reverse after discontinuation.
- Storage. Vyleesi autoinjectors: room temperature, protect from light. Compounded lyophilized: refrigerate before reconstitution and after.
- Compounded vs approved. "PT-141" sold through compounding pharmacies and research channels is not Vyleesi. The active ingredient is the same; the quality system, formulation, and labeling are not.
Sources
- 1.Kingsberg SA et al. (2019). Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials (RECONNECT). Obstetrics & Gynecology.
- 2.Dhillon S, Keam SJ (2019). Bremelanotide: First Approval. Drugs.
- 3.FDA Prescribing Information — Vyleesi (bremelanotide) injection.
- 4.Diamond LE et al. (2006). An effect on the subjective sexual response in premenopausal women with sexual arousal disorder by bremelanotide (PT-141). Journal of Sexual Medicine.