PT-141 (Bremelanotide)
A melanocortin agonist that acts centrally — not a vascular compound.
Endocrine · 6 min read · updated 13 Aug 2026
Research use only. The ranges below are what published studies and community protocols report. They are reference material for laboratory research, not medical advice or a recommendation for human or veterinary use.
The compound
PT-141
View- Type
- Melanocortin Receptor Agonist
- CAS
- 189691-06-3
- Formula
- C₅₀H₆₈N₁₄O₁₀
- Mass
- 1025.18 g/mol
At a glance
- Class
- Melanocortin receptor agonist (MC3R / MC4R)
- Molecular weight
- 1025.18 g/mol
- CAS
- 189691-06-3
- Derived from
- A metabolite of melanotan II
- Regulatory status
- Approved as Vyleesi for HSDD in premenopausal women
- Approved dose
- 1.75 mg subcutaneous, as needed
- Vial size stocked
- 10 mg
PT-141 is a cyclic heptapeptide that emerged from work on melanotan II. Melanotan II is a broad melanocortin agonist that produces tanning through MC1R alongside its other effects; the metabolite that became bremelanotide retains activity at MC3R and MC4R with much weaker MC1R activity, which separates the central effects from the pigmentation.
What makes it mechanistically distinct from every other compound in this space is where it acts. PDE5 inhibitors work peripherally on vascular smooth muscle — they amplify a signal that arousal has already generated. PT-141 acts in the hypothalamus, on MC4R-expressing neurons in the paraventricular nucleus, upstream of the vascular event. It works on the initiating signal rather than the plumbing.
It is an approved medicine, which puts it in a small minority here. The approval is narrow — hypoactive sexual desire disorder in premenopausal women, at 1.75 mg subcutaneously as needed — but it means there is a real dossier of controlled safety and efficacy data behind the dose.
Mechanism in detail
- MC4R in the paraventricular nucleus of the hypothalamus is the principal target; activation there engages the central pathways that initiate sexual arousal, including downstream dopaminergic signalling in the medial preoptic area.
- MC3R contributes, though its role is less clearly delineated.
- MC1R activity is weak but not zero — which is why repeated high-dose use can still produce gradual skin darkening and increased freckling over time.
- Because the mechanism is central and not vascular, it does not depend on nitric oxide signalling and is not additive with PDE5 inhibition in the way two vascular agents would be. It is also why the reported time to onset is measured in tens of minutes to hours rather than minutes.
The nausea problem
Nausea is the defining tolerability issue and it is common — reported in roughly 40% of subjects in the registration trials at 1.75 mg, with about 1 in 20 (~4.8%) experiencing vomiting. MC4R is expressed in brainstem regions involved in emesis, so this is on-target, not an impurity effect.
It is also dose-dependent, which is why reported research protocols frequently start well below the approved 1.75 mg — often at 0.5 mg — and titrate. Halving the dose meaningfully reduces the nausea rate at some cost to effect.
Blood pressure
Bremelanotide produces a transient rise in blood pressure and a small reduction in heart rate, peaking within a few hours of administration and resolving within about half a day. The magnitude is modest in the trial population but it is a documented, reproducible effect and the reason uncontrolled hypertension and established cardiovascular disease are exclusions in the approved labelling.
This is also why the approved schedule caps use at one dose in 24 hours and no more than eight per month — the limit is about cumulative cardiovascular exposure, not tachyphylaxis.
Storage
- Lyophilised: 2–8 °C, or −20 °C for extended storage, protected from light.
- Reconstituted: 2–8 °C, used within about 28 days. Never freeze.
- Episodic use makes the date label essential — it is easy to lose track of when a rarely-used vial was opened.
Cautions
- Nausea affects a large minority at the approved dose and is the main reason for dose reduction.
- Transient blood-pressure elevation is documented; uncontrolled hypertension and cardiovascular disease are exclusions in the approved labelling.
- Residual MC1R activity means gradual hyperpigmentation and increased freckling with repeated use, particularly in darker skin types. This is cumulative and only partially reversible.
- The monthly cap in the approved schedule exists for a reason and is a sensible ceiling in any research protocol.
- Flushing and headache are common and generally short-lived.
References & credit
- 1Kingsberg SA et al., Obstetrics & Gynecology 2019 — RECONNECT — the phase 3 bremelanotide trials underpinning the approved dose.
- 2Clayton AH et al., Womens Health (Lond) 2016 — Bremelanotide safety and the cardiovascular profile.
- 3Molinoff PB et al., Ann N Y Acad Sci 2003 — PT-141 and the central melanocortin mechanism of sexual arousal.
This article was written in-house. Where a dose range reflects community practice rather than a published trial, the community references we consulted are credited above and the article says which is which.