PT-141
Melanocortin receptor agonist (cyclic heptapeptide analog of α-MSH)
- Class
- Melanocortin agonist
- Half-life
- ~2.7 hours
- Route
- Subcutaneous (SubQ)
- Cadence
- Multiple per week
- Evidence
- Human clinical trials
Overview
PT-141 (bremelanotide) is the first FDA-approved on-demand treatment for low sexual desire in premenopausal women — and one of the only peptides that works by hitting the brain instead of blood vessels. You inject it subcutaneously about 45 minutes before anticipated sexual activity, and it activates melanocortin receptors in the hypothalamus — the circuits that drive arousal and desire upstream of any physical response. FDA-approved as Vyleesi in 2019 for acquired, generalized hypoactive sexual desire disorder (HSDD), though off-label use in men is common.
The mechanism is fundamentally different from drugs like Viagra or Cialis. Those work by enhancing blood flow after arousal is already present. PT-141 works earlier in the chain — it generates the arousal itself by hitting MC3R and MC4R receptors in the brain. The result is increased sexual desire and reduced distress about low libido, measured in two identical Phase 3 trials (RECONNECT 1 and 2) involving 1,247 premenopausal women over 24 weeks. About 25% of women on PT-141 saw a meaningful increase in desire scores, versus 17% on placebo.
The catch: nausea is extremely common — 40% of trial participants, versus 1% on placebo. It's usually mild to moderate and improves after the first dose or two, but about 18% of people quit the trials because of side effects (mostly nausea, vomiting, or flushing). There's also a transient blood pressure increase of 2-3 mmHg lasting a few hours after each dose — not dangerous for most people, but a hard no if you have uncontrolled hypertension or cardiovascular disease.
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
- Nausea is the dominant side effect — 40% of trial participants. Median onset within 1 hour post-dose, lasting ~2 hours. Often improves after the first dose. Ondansetron or other antiemetics can help if it's intolerable.
- Transient blood pressure increase: mean +1.9 mmHg systolic and +1.7 mmHg diastolic based on ambulatory monitoring. Peak increases occur 4-8 hours post-dose and are transient (back to baseline within 12 hours). Hard contraindication if you have uncontrolled hypertension or known cardiovascular disease.
- Skin hyperpigmentation (face, gums, breasts) occurs in some users due to MC1R activation. Can be permanent. More common in people with darker baseline skin tone and with frequent dosing (>8 doses/month).
+ 3 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching PT-141.
- Blood pressure — measure before starting and periodically during use (contraindicated if uncontrolled)
- Skin pigmentation changes (gums, face, breasts) — can be permanent even after stopping
- Nausea severity and pattern — track whether it improves after first 1-2 doses
- Subjective arousal and desire — the actual target endpoint
- Cardiovascular symptoms (dizziness, palpitations, flushing)
- Injection site reactions (pain, bruising, redness)
Frequently asked questions
What is PT-141?
Melanocortin receptor agonist (cyclic heptapeptide analog of α-MSH). PT-141 (bremelanotide) is the first FDA-approved on-demand treatment for low sexual desire in premenopausal women — and one of the only peptides that works by hitting the brain instead of blood vessels. You inject it subcutaneously about 45 minutes before anticipated sexual activity, and it activates melanocortin receptors in the hypothalamus — the circuits that drive arousal and desire upstream of any physical response. FDA-approved as Vyleesi in 2019 for acquired, generalized hypoactive sexual desire disorder (HSDD), though off-label use in men is common.
How is PT-141 administered?
Subcutaneous (SubQ), typically multiple per week.
What is the half-life of PT-141?
~2.7 hours — Clears quickly from plasma, but arousal effects last 6-8 hours post-dose.
Is PT-141 approved for human use?
PT-141 is investigational — not approved by the FDA, EMA, or MHRA for human use at the time of writing.
What does the evidence show for PT-141?
Evidence tier: Human clinical trials. Two identical Phase 3 trials (NCT02333071, NCT02338960) enrolled 1,247 premenopausal women with HSDD for 24 weeks. About 25% of women on 1.75 mg PT-141 had a ≥1.2-point increase in sexual desire score (range 1.2-6.0) vs 17% on placebo.
What is commonly monitored when researching PT-141?
Commonly tracked markers + signals: Blood pressure — measure before starting and periodically during use (contraindicated if uncontrolled), Skin pigmentation changes (gums, face, breasts) — can be permanent even after stopping, Nausea severity and pattern — track whether it improves after first 1-2 doses, Subjective arousal and desire — the actual target endpoint, Cardiovascular symptoms (dizziness, palpitations, flushing), Injection site reactions (pain, bruising, redness).
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.