PT-141 (bremelanotide) is a peptide medicine that works through brain melanocortin pathways involved in sexual desire - not by changing blood flow like Viagra. It is FDA-approved as Vyleesi for certain premenopausal women with distressing low sexual desire (HSDD), but it is not approved for men, postmenopausal women, or sexual performance enhancement.
Bremelanotide is an on-demand subcutaneous melanocortin receptor agonist approved for acquired, generalized HSDD in premenopausal women, after exclusion of medical, psychiatric, medication, substance, or relationship causes. The anchor protocol is 1.75 mg SC at least 45 minutes before anticipated sexual activity, max once daily and not more than 8 times monthly, with monitoring for BP/HR effects, nausea, flushing, headache, injection reactions, and hyperpigmentation.
Bremelanotide is a synthetic cyclic heptapeptide, Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH, acting as a nonselective melanocortin agonist with clinically relevant MC1R and MC4R activity. Its HSDD effect is presumed to involve central MC4R-associated sexual desire/arousal circuitry, while key safety signals map to MC1R melanogenesis, central/autonomic BP/HR effects, GI motility changes, and nausea pathways - and it was derived from the broader melanocortin agonist Melanotan II.
PT-141 is one of the highest-evidence entries in this atlas: it has an FDA-approved product (Vyleesi), label-defined PK and safety, and two phase 3 RCTs behind its approved indication. That makes the editorial job different - here the discipline is keeping the narrow approved use (premenopausal HSDD, women) cleanly separated from the much larger off-label space (men, performance, custom vials, intranasal, daily use, stacks), which drops to Grade D/P.
PT-141 is different from Viagra-type drugs. Instead of increasing blood flow to the genitals, it works in the brain - on melanocortin pathways tied to sexual desire and arousal. That central action is also why its side effects (nausea, blood-pressure changes, skin darkening) come from the same receptor family acting in other parts of the body.
Bremelanotide is a nonselective melanocortin receptor agonist. The desire effect is attributed to central MC4R signaling, while MC1R activity on melanocytes drives the hyperpigmentation risk and central/autonomic melanocortin tone underlies the transient BP rise, HR reduction, and nausea. The FDA label is explicit that the exact HSDD mechanism is not fully known.
MC4R is a GPCR involved in neuroendocrine, autonomic, reward, and energy-balance signaling, coupling through cAMP/PKA and additional β-arrestin / pathway-biased routes. Bremelanotide's effect is presumed to act through MC4R-expressing neurons distributed across hypothalamic and extra-hypothalamic CNS regions - the same circuitry that links it to weight/intake exploratory work.
PT-141 has exactly one high-confidence protocol: the FDA-approved Vyleesi label. Everything else - custom vials, male ED use, intranasal, lower titration ladders, daily use, or stacks - is off-label or speculative and graded D/P unless tied directly to a human trial. The page keeps the approved protocol visually distinct from the research models below it. Working unit: µg.
| Band | Dose | ~µg/kg at 70 kg | Basis / grade |
|---|---|---|---|
| Micro / tolerability | 250-500 µg | 3.6-7.1 | Speculative custom-vial screening band - D |
| Low research | 500-1000 µg | 7.1-14.3 | Extrapolated SC model below the FDA dose - D |
| Label-equivalent | 1750 µg | ~25 | FDA-approved Vyleesi dose - A |
| Above-label | >1750 µg | >25 | Not recommended; raises BP/nausea/pigmentation - D / hard caution |
The FDA dose is fixed, not weight-based; only the 1750 µg label-equivalent is Grade A. All other bands are educational models.
| Body weight | 250 µg | 500 µg | 1000 µg | 1750 µg (label) |
|---|---|---|---|---|
| 55 kg | 4.5 µg/kg | 9.1 µg/kg | 18.2 µg/kg | 31.8 µg/kg |
| 65 kg | 3.8 µg/kg | 7.7 µg/kg | 15.4 µg/kg | 26.9 µg/kg |
| 75 kg | 3.3 µg/kg | 6.7 µg/kg | 13.3 µg/kg | 23.3 µg/kg |
| 85 kg | 2.9 µg/kg | 5.9 µg/kg | 11.8 µg/kg | 20.6 µg/kg |
| 95 kg | 2.6 µg/kg | 5.3 µg/kg | 10.5 µg/kg | 18.4 µg/kg |
| 105 kg | 2.4 µg/kg | 4.8 µg/kg | 9.5 µg/kg | 16.7 µg/kg |
The FDA dose is fixed; this table is for calculator/education context only.
| Trigger | Action | Rationale |
|---|---|---|
| Nausea >2-4 h, vomiting, severe headache | Hold or reduce; clinical review | Recognized common AEs |
| Meaningful BP rise or uncontrolled hypertension | HARD STOP / contraindication review | Contraindicated in uncontrolled HTN or known CVD |
| Skin / mucosal darkening | STOP and evaluate | Focal hyperpigmentation may not fully resolve |
| No benefit after 8 weeks | Discontinue | Label says discontinue after 8 weeks without improvement |
| Need >8 uses/month | Do not escalate; reassess diagnosis | >8/month raises BP & pigmentation exposure |
| Uses oral naltrexone (alcohol/opioid) | Avoid combination | May significantly reduce naltrexone exposure |
| Pregnancy suspected | HARD STOP | Animal fetal-harm signal |
| Measure | Use | Validated for PT-141? |
|---|---|---|
| Blood pressure | Safety | Yes - label-recognized BP increase |
| Heart rate | Safety | Yes - label-recognized HR reduction |
| Skin / mucosal pigmentation log | Safety | Yes - face, gingiva, breasts noted in label |
| FSFI-Desire domain | Clinical outcome | Yes - phase 3 trial endpoint |
| FSDS-DAO Q13 | Clinical distress outcome | Yes - phase 3 trial endpoint |
| Testosterone / prolactin / estradiol | Differential workup context | No - not PT-141 response markers |
| Liver enzymes | Safety context | Not routine - one acute-hepatitis OLE case, causality unclear |
For research-vial reconstitution math only. The FDA-approved product is a prefilled 1.75 mg / 0.3 mL autoinjector that needs no reconstitution - this calculator is educational modeling, not clinical dose selection. Formula: concentration = vial µg / BAC mL; draw mL = target µg / concentration; U-100 units = draw mL x 100; doses = vial µg / target µg.
The approved product is a prefilled Vyleesi autoinjector (1.75 mg / 0.3 mL = 5833 µg/mL) and needs no reconstitution. This calculator models research-vial math only - it is not clinical dose selection, and the 1750 µg label-equivalent is the only Grade-A anchor. Use outside the approved protocol (men, daily use, custom vials, intranasal) is off-label/speculative, and bremelanotide is contraindicated in uncontrolled hypertension or known cardiovascular disease.
Keep the Grade-A Vyleesi protocol (prefilled, 1.75 mg SC) visually separate from any custom-vial or off-label modeling.
Contraindicated in uncontrolled hypertension or known CVD - the single most important screening step before any use.
~40% incidence; ondansetron pretreatment did not reduce it in a phase 4 study - set expectations rather than relying on anti-emetics.
Hyperpigmentation rises sharply with daily/frequent use; the 8/month cap is a safety limit, not arbitrary.
Avoid with oral naltrexone for alcohol/opioid addiction - reduced exposure could cause treatment failure.
Compounded bremelanotide is not the FDA-approved product absent lawful pharmacy/prescriber frameworks; verify identity/quality.
PT-141 combinations are mechanistically interesting but largely off-label and unapproved as combinations. The most-discussed pairing (with PDE5 inhibitors) targets a real complementary axis - central desire plus peripheral erectile hemodynamics - but cardiovascular review is essential, and the naltrexone interaction is a firm label-level hard stop.
Do not use or stack PT-141 in patients with uncontrolled hypertension or known cardiovascular disease, and avoid oral naltrexone products for alcohol/opioid addiction, because bremelanotide may significantly decrease naltrexone exposure. The cardiovascular gate applies to every combination - the PDE5 pairing in particular requires careful CV and nitrate review. Off-label and combination uses carry thinner evidence than the approved HSDD indication and should be framed accordingly.
Unusually for this atlas, PT-141's safety profile is label-defined from controlled trials rather than inferred. Nausea is dominant (~40% vs 1.3% placebo), with flushing, headache, injection-site reactions, a modest transient BP rise / HR drop, and focal hyperpigmentation. The cardiovascular contraindication is the central gate, and frequency limits exist specifically to bound pigmentation and BP exposure.
| Condition | Concern | Severity |
|---|---|---|
| Uncontrolled hypertension | Contraindicated due to BP increase | High |
| Known cardiovascular disease | Contraindicated | High |
| High cardiovascular risk | Not recommended | High |
| Pregnancy / suspected pregnancy | Discontinue; animal fetal-harm signal | High |
| Oral naltrexone (alcohol/opioid addiction) | Reduced naltrexone exposure → treatment failure | High |
| Need for daily / frequent use | Frequency raises pigmentation & BP exposure | High |
| Severe renal impairment | Exposure increases - use caution | Moderate-High |
| Severe hepatic impairment | Not studied - use caution | Moderate-High |
| History of severe nausea/vomiting | High nausea incidence | Moderate |
| Darker skin / pigmentation concern | Higher hyperpigmentation risk | Moderate |
The primary safety monitoring - label-recognized transient rise in BP and reduction in HR; screen CV status first.
Set expectations (~40%); ondansetron pretreatment is not recommended based on phase 4 data.
Face, gingiva, and breasts noted in the label; track and stop if darkening develops.
FSFI-Desire and FSDS-DAO Q13 are the validated endpoints; discontinue after 8 weeks if no improvement.
Avoid oral naltrexone; account for slowed oral-drug absorption from reduced gastric motility.
No more than 1 dose/24 h and 8/month - exceeding this is a do-not-escalate signal.
PT-141 has an unusually strong evidence base for a peptide page: an FDA-approved product, label-defined PK/safety, and two phase 3 RCTs for premenopausal acquired generalized HSDD. The evidence becomes much thinner for male ED, custom-vial protocols, intranasal use, body-composition/metabolic use, and stacking - those areas remain off-label, historical, exploratory, or speculative.
Two phase 3 randomized, double-blind, placebo-controlled trials (1267 randomized in the label summary) of 1.75 mg SC PRN showed significant improvement in FSFI-Desire and FSDS-DAO Q13 vs placebo, with no significant difference in satisfying sexual events.
The RECONNECT phase 3 trials reported improved sexual desire and related distress with 1.75 mg SC PRN in premenopausal women with HSDD - a substantially higher evidence standard than most peptides in clinical use.
A randomized placebo-controlled dose-finding trial (397 randomized) of SC 0.75/1.25/1.75 mg showed efficacy/safety signals in premenopausal female sexual dysfunction, informing the phase 3 dose selection.
Double-blind placebo-controlled work characterized intranasal PT-141 PK/PD, with significant erectile response at doses >7 mg, and a separate study evaluated ED patients who had failed sildenafil - both off-label, historical routes.
A phase 4 single-dose study (n=228) found ondansetron pretreatment did not reduce nausea, and a neurobiology review details bremelanotide's central mechanism in HSDD.
Melanocortin receptors signal through G-protein and non-G-protein pathways, with complex pathway-biased MC4R pharmacology; melanocortins are linked to penile-erection physiology; and an exploratory analysis examined bremelanotide's effect on body weight in obese women.
PT-141 / bremelanotide has an unusually strong evidence base for a peptide page - an FDA-approved product, label-defined PK/safety, and phase 3 RCT evidence for premenopausal acquired generalized HSDD. The evidence is much thinner for male ED, custom-vial protocols, intranasal use, body-composition / metabolic use, and stacking (historical intranasal ED data, exploratory weight analysis), which should remain clearly labeled as off-label, historical, exploratory, or speculative. An honest read: the approved indication is genuinely Grade A, and the popular off-label uses borrow credibility from it without sharing its evidence.
| Study / source | Design | Route / dose | Outcome | Grade |
|---|---|---|---|---|
| Vyleesi label (phase 3) | 2 RCTs, n=1267 | SC 1.75 mg PRN | ↑ desire/distress; no Δ in satisfying events | A |
| Kingsberg 2019 (RECONNECT) | 2 phase 3 RCTs | SC 1.75 mg PRN | Improved desire & distress | A |
| Clayton 2016 | Phase 2b, n=397 | SC 0.75/1.25/1.75 mg | Dose-ranging efficacy/safety | B |
| Intranasal ED trial | DB placebo-controlled | Intranasal >7 mg | Significant erectile response | B |
| Sildenafil-failure study | RCT | Intranasal | Evaluated PDE5 non-responders | B |
| Phase 4 nausea/ondansetron | RCT, n=228 | Ondansetron + SC 1.75 mg | No nausea reduction | B |
| Weight exploratory | Analysis | SC | MC4R activity & intake/weight signal | C/D |
Two useful axes: against the other approved HSDD drug (flibanserin - oral, daily, serotonergic vs PT-141's on-demand central melanocortin action), and against the melanocortin family it comes from (Melanotan II, its less-selective tanning-associated parent; setmelanotide, a selective MC4R agonist approved for rare genetic obesity).
| Feature | PT-141 / Bremelanotide | Flibanserin | Melanotan II | Setmelanotide |
|---|---|---|---|---|
| Primary use | HSDD (premenopausal women) | HSDD (premenopausal women) | Tanning / sexual effects (research) | Rare genetic obesity |
| Mechanism class | Melanocortin agonist (MC4R) | Serotonergic CNS modulator | Nonselective melanocortin agonist | MC4R agonist (selective) |
| Dosing | On-demand SC, PRN | Oral, daily | SC / intranasal (gray-market) | SC, daily |
| Evidence tier | Phase 3 + FDA label | FDA-approved | Mostly non-approved / research | FDA-approved (specific genetics) |
| Regulatory status | FDA-approved (Vyleesi) | FDA-approved | Not FDA-approved | FDA-approved (rare obesity) |
| Key caution | BP/CVD, nausea, pigmentation | Hypotension / alcohol interaction | Pigmentation/tanning; unregulated | Hyperpigmentation; indication-specific |