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AMIRAVOResearch Library

PT-141 (Bremelanotide) vs Oxytocin

PT-141 and oxytocin are both FDA-approved peptide medicines, but for entirely different indications 1,5. PT-141, bremelanotide, is a melanocortin receptor agonist approved in 2019 as VYLEESI for premenopausal women with acquired, generalised hypoactive sexual desire disorder 1. Oxytocin is a nine-amino-acid hormone whose approved injectable products, including Pitocin, are indicated for initiation or improvement of uterine contractions in labour and for related obstetric uses 5,6. Comparisons between them usually come from interest in oxytocin's reported social and behavioural effects, which are not an approved use, and where a large randomised trial in autism was negative 8,9.

Unbranded reference vial illustrating PT-141; not an actual product
PT-141
FDA-approved
Unbranded reference vial illustrating Oxytocin; not an actual product
Oxytocin
FDA-approved

Side by side

FieldPT-141Oxytocin
ClassSynthetic cyclic 7-amino-acid melanocortin receptor agonist 1Nine-amino-acid peptide hormone; oxytocin receptor agonist 6,7
Origin and structureMelanocortin analogue developed from the alpha-MSH line of research 3,4Endogenous hormone made in the hypothalamus; the approved product is synthetic oxytocin injection 6,7
Proposed mechanismLabel: nonselectively activates several melanocortin receptor subtypes, with MC1R and MC4R binding most relevant; the mechanism of its effect in this disorder is stated to be unknown 1Label: increases intracellular calcium in myometrium, promoting uterine contraction; receptor numbers rise in pregnancy 6
Half-lifeMean terminal half-life about 2.7 hours (range 1.9 to 4.0) after a single subcutaneous dose 1Plasma half-life about 1 to 6 minutes, decreased in late pregnancy and lactation 6
Highest human trial phasePhase 3: two identical randomised, double-blind, placebo-controlled trials (RECONNECT) randomising 1,267 women, plus a 52-week open-label extension 2,10Long-established approved obstetric use; also tested in a 24-week phase 2 randomised trial of the intranasal form in 290 children and adolescents with autism 8,9
FDA statusFDA-approved 2019 as VYLEESI (bremelanotide injection); label version dated 13 November 2025 1FDA-approved; Drugs@FDA lists several oxytocin injection applications in prescription status, including NDA 018243 and ANDA 200219, queried 24 October 2026 5; Pitocin label version dated 12 August 2024 6
Published human outcomesIn the phase 3 trials, desire scores rose and distress scores fell versus placebo, with integrated changes of 0.35 and -0.33 on the two coprimary scales 2Approved obstetric uses are established in the label 6. For social behaviour, the SOARS-B trial found no significant difference from placebo on its primary social-withdrawal measure 8
Safety signalsNausea, flushing and headache in 10% or more; label warns of transient blood pressure rise with heart-rate fall and of focal hyperpigmentation 1,2Label restricts labour use to intravenous administration under hospital supervision with continuous observation, and notes inherent pressor and antidiuretic properties at large doses 6
WADA statusNot named on the 2026 Prohibited List 11Not named on the 2026 Prohibited List 11
Who funded the evidenceThe phase 3 trials and extension were funded by Palatin Technologies and AMAG Pharmaceuticals 2,10The autism trial was funded by the National Institute of Child Health and Human Development 8

PT-141: what the data says

Bremelanotide (PT-141) is a melanocortin receptor agonist approved in 2019 for premenopausal women with acquired, generalised hypoactive sexual desire disorder; the label states that the mechanism of its effect in this condition is unknown 1. Its mean terminal half-life after a single subcutaneous dose is about 2.7 hours 1.

Approval rested on two identical phase 3 randomised, double-blind, placebo-controlled trials (RECONNECT) that randomised 1,267 premenopausal women to 24 weeks of bremelanotide or placebo 2. Both coprimary endpoints favoured bremelanotide, with integrated changes of 0.35 on the desire domain and -0.33 on the distress item, and more nausea, flushing and headache than placebo 2. In the 52-week open-label extension, 684 of 856 eligible patients enrolled and 272 completed; the most common drug-related events were nausea (40.4%), flushing (20.6%) and headache (12.0%) 10. The label warns of a transient blood pressure rise with heart-rate fall after each dose and of focal hyperpigmentation 1.

Oxytocin: what the data says

Oxytocin is a nine-amino-acid hormone made in the hypothalamus, acting on oxytocin receptors; a 2018 review describes its receptor signalling and its roles in reproduction and social behaviour in animal and human studies 7. The approved injectable products are indicated for initiation or improvement of uterine contractions where vaginal delivery is considered suitable, and the label states that oxytocin is not indicated for elective induction of labour 6. Its plasma half-life is about 1 to 6 minutes 6.

Beyond obstetrics, the largest randomised test of its behavioural effects was negative: in the SOARS-B phase 2 trial, 290 children and adolescents with autism spectrum disorder received intranasal oxytocin or placebo for 24 weeks, and the change on the primary social-withdrawal measure was -3.7 with oxytocin versus -3.5 with placebo, with secondary outcomes generally not differing 8. Adverse events were similar between groups in that trial 8.

Key research differences

  • Indication: bremelanotide is approved for hypoactive sexual desire disorder in premenopausal women 1, while oxytocin's approved injectable use is obstetric 6.
  • Receptor target: bremelanotide acts at melanocortin receptors 1, whereas oxytocin acts at the oxytocin receptor 6,7.
  • Half-life: about 2.7 hours for bremelanotide versus about 1 to 6 minutes for oxytocin 1,6.
  • Evidence for behavioural effects: bremelanotide has two positive phase 3 trials on desire scales 2, whereas the largest randomised trial of intranasal oxytocin for social behaviour found no difference from placebo 8.
  • Monitoring: oxytocin's label requires hospital administration under continuous observation for labour use 6, while the bremelanotide label centres on blood-pressure and pigmentation cautions 1.

Where the evidence is limited

No study has compared bremelanotide with oxytocin. They are approved for different conditions, in different populations, and by different routes, so their trial results are not interchangeable 1,6. Oxytocin's reported social and sexual effects come from research use of the intranasal form rather than an approved indication, and the largest such trial was negative 8. The bremelanotide trials measured changes on desire and distress questionnaires over 24 weeks, which is a different kind of endpoint from the obstetric outcomes in oxytocin's label 2,6.

Frequently asked questions

Is PT-141 the same as bremelanotide and VYLEESI?
Yes. PT-141 is the development name for bremelanotide, marketed as VYLEESI, approved in 2019 1,4.
Is oxytocin approved for sexual desire or bonding?
No. Its approved injectable indications are obstetric 6. The largest randomised trial of intranasal oxytocin for social behaviour, in autism, found no difference from placebo 8.
Can PT-141 and oxytocin be compared directly?
Not meaningfully. No head-to-head study exists, and they are approved for different conditions with different receptor targets 1,6.
What side effects were most common with bremelanotide?
Nausea, flushing and headache, each in 10% or more of participants in the phase 3 trials, with nausea in 40.4% during the open-label extension 2,10. The label also warns of transient blood-pressure increases and focal hyperpigmentation 1.

References

  1. VYLEESI (bremelanotide injection) prescribing information (label version dated 13 November 2025) DailyMed. 2025
  2. Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials Obstetrics & Gynecology. 2019
  3. PT-141: a melanocortin agonist for the treatment of sexual dysfunction Annals of the New York Academy of Sciences. 2003
  4. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization Peptides. 2006
  5. Drugs@FDA via openFDA: application records for oxytocin injection, including NDA 018243 and ANDA 200219 in prescription status (queried 24 October 2026) openFDA. 2026
  6. PITOCIN (oxytocin injection, USP) prescribing information (label version dated 12 August 2024) DailyMed. 2024
  7. The Oxytocin Receptor: From Intracellular Signaling to Behavior Physiological Reviews. 2018
  8. Intranasal Oxytocin in Children and Adolescents with Autism Spectrum Disorder (SOARS-B) New England Journal of Medicine. 2021
  9. Oxytocin: the great facilitator of life Progress in Neurobiology. 2009
  10. Long-Term Safety and Efficacy of Bremelanotide for Hypoactive Sexual Desire Disorder Obstetrics & Gynecology. 2019
  11. Prohibited List (2026 List, in force 1 January 2026) World Anti-Doping Agency. 2026

For research use only. Not for human or veterinary use. Not a drug, food, or dietary supplement. This page compares published research and is not medical advice or a recommendation.