PT-141 (Bremelanotide) Dosage Protocol

In short: PT-141 is the active ingredient in Vyleesi, FDA-approved for female HSDD at a fixed 1.75 mg subcutaneous dose — and it's also widely sold off-label through compounding and research-chem channels.

Bremelanotide, sold under the brand name Vyleesi, secured FDA approval on June 21, 2019 for the treatment of acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women at a fixed subcutaneous dose of 1.75 mg administered at least 45 minutes before anticipated sexual activity [1]. It is one of only two FDA-approved therapies for female HSDD and the only melanocortin-receptor agonist in that class.

Reported protocols in the peer-reviewed literature fall into two categories: the approved 1.75 mg subcutaneous autoinjector regimen, and earlier investigational intranasal protocols that ranged from 7.5 mg to 20 mg per dose before the development program pivoted to subcutaneous administration over cardiovascular concerns [2].

How PT-141 Works: Mechanism of Action

In short: PT-141 activates melanocortin-4 receptors in the hypothalamus, which sit upstream of the dopamine circuits that regulate sexual desire — this is a central-nervous-system drug, not a blood-flow drug like Viagra.

Bremelanotide is a cyclic seven-amino-acid peptide analog of alpha-melanocyte-stimulating hormone (α-MSH). It is a non-selective melanocortin receptor agonist with functional activity at MC1R, MC3R, MC4R, and MC5R, with the MC4R activity in hypothalamic nuclei considered central to its pro-sexual effects [3]. MC4R expression in the medial preoptic area and paraventricular nucleus places the peptide upstream of dopaminergic circuits that govern sexual motivation, which is why bremelanotide is classified as a central-acting agent rather than a peripheral vasoactive drug like phosphodiesterase-5 inhibitors.

The pivotal RECONNECT Phase 3 program enrolled 1,247 premenopausal women with acquired, generalized HSDD across two identical randomized, double-blind, placebo-controlled trials. Women who received 1.75 mg subcutaneous bremelanotide reported statistically significant improvements on the Female Sexual Function Index - Desire domain and the Female Sexual Distress Scale - Desire/Arousal/Orgasm item 13, with effect sizes described as modest but consistent across both studies [4]. These outcomes formed the basis of the 2019 FDA approval.

Pharmacokinetic modeling from labeled and pre-approval data gives a time-to-peak-plasma-concentration (Tmax) of approximately 1.0 hour after subcutaneous injection in the thigh or abdomen, a mean terminal half-life of roughly 2.7 hours, and a volume of distribution of about 25 L, consistent with limited tissue penetration relative to body weight [1]. Food does not meaningfully affect absorption because the route is subcutaneous. Melanocortin receptor agonism also drives the dose-limiting adverse events: nausea, transient blood-pressure elevation, and focal hyperpigmentation [1,4].

Earlier intranasal development by Palatin Technologies was halted in 2008 after several healthy-volunteer studies found increases in systolic blood pressure exceeding 15 mm Hg at doses above 10 mg intranasally [2]. That finding reshaped the entire program, pushing the sponsor toward the lower subcutaneous 1.75 mg dose that carries a narrower blood-pressure signal but still requires warnings in the approved label about same-day use restrictions.

PT-141 Dose Ranges in the Peer-Reviewed Literature

In short: the approved dose is 1.75 mg subcutaneously, on-demand, capped at 8 doses a month — every other reported protocol is either a dose-finding study or an abandoned intranasal arm.

Published community self-report protocols for off-label male sexual-function use generally describe 1.0–2.0 mg subcutaneously timed several hours before activity, mirroring the FDA dose. Those protocols are not validated in men by any controlled trial of the subcutaneous route for erectile or libido outcomes.

PT-141 Reconstitution: Math and Worked Examples

In short: Vyleesi ships pre-filled at 1.75 mg / 0.3 mL and requires no math. Research-chem vials need BAC water and a concentration table — how much water you add determines the "unit" count on an insulin syringe.

Bremelanotide in research-chemical form is typically supplied as a lyophilized powder in 5 mg or 10 mg vials. The FDA-approved product (Vyleesi) is a pre-filled autoinjector delivering 1.75 mg in 0.3 mL and does not require reconstitution.

Formula: Concentration (mg/mL) = Vial peptide (mg) ÷ BAC water (mL)

10 mg vial, 2 mL BAC water:

• Concentration = 10 mg ÷ 2 mL = 5 mg/mL
• For a 1.75 mg dose: 1.75 ÷ 5 = 0.35 mL = 35 units on a U-100 insulin syringe
• For a 1.0 mg dose: 1.0 ÷ 5 = 0.20 mL = 20 units
• For a 0.5 mg titration dose: 0.5 ÷ 5 = 0.10 mL = 10 units

5 mg vial, 2 mL BAC water:

• Concentration = 5 mg ÷ 2 mL = 2.5 mg/mL
• For a 1.75 mg dose: 1.75 ÷ 2.5 = 0.70 mL = 70 units (practically at the upper limit of a standard 1 mL insulin syringe; consider reconstituting with 1 mL BAC for a 5 mg/mL working solution)

5 mg vial, 1 mL BAC water:

• Concentration = 5 mg/mL
• 1.75 mg dose = 0.35 mL = 35 units

Reconstituted bremelanotide is generally described in stability literature as chemically stable for approximately 28 days under refrigeration at 2–8 °C when using bacteriostatic water, based on general cyclic-peptide stability data. Published peer-reviewed stability studies for bremelanotide specifically are limited.

PT-141 Administration, Titration, and Dosing Schedule

In short: subcutaneous into the abdomen or thigh, at least 45 minutes before anticipated activity, and no more than one dose per day or eight per month.

The approved subcutaneous route uses an autoinjector delivering the fixed 1.75 mg dose into the abdomen or thigh. The FDA label specifies administration at least 45 minutes before anticipated sexual activity, based on Tmax of roughly 1 hour and pharmacodynamic modeling of desire outcomes in RECONNECT [1,4]. Injection-site rotation is encouraged because focal hyperpigmentation has been reported at sites of repeated injection, particularly in patients with Fitzpatrick skin types III–VI.

The label restricts dosing to no more than one 1.75 mg dose per 24-hour period and no more than eight doses per month. The 30-day cap is based on cumulative exposure modeling and the observed blood-pressure signal rather than a specific toxicity threshold [1]. Alcohol is not contraindicated but is discouraged because nausea, the most common adverse event, is exacerbated.

For intranasal administration (investigational only, no longer in active development), reported dosing used a metered-dose sprayer delivering 4–20 mg per administration, with absorption more variable and a faster but less predictable onset than the subcutaneous route [2,6].

Standard U-100 insulin syringes with 29–31 gauge, 5/16-inch needles are the research-setting norm for subcutaneous administration of reconstituted bremelanotide in published case series. The abdomen (avoiding 2 inches around the umbilicus) and the anterior thigh are the most commonly described injection sites. Timing relative to meals has not been shown to affect pharmacokinetics or clinical response, although heavy meals prior to dosing may compound the nausea signal that is the principal dose-limiting adverse event. Some clinical pharmacology data suggest that taking the dose in a semi-recumbent posture reduces the subjective nausea peak, although this has not been formally randomized.

PT-141 Cycle Structure and Protocol Duration

In short: PT-141 is on-demand, not cycled. The monthly cap and receptor-desensitization concerns are the main reasons daily dosing was never developed.

Bremelanotide is an on-demand medication rather than a cycled peptide. The RECONNECT Phase 3 trials dosed participants for 24 weeks on-demand with a monthly cap, and open-label extensions ran out to 52 weeks without evidence of tachyphylaxis to the desire-domain effect [4,8]. No formal washout period is defined in the label.

The pharmacologic rationale for on-demand rather than daily dosing rests on two mechanisms documented in the pre-approval package. First, chronic MC4R occupancy in rodent models leads to measurable receptor downregulation within 7–14 days [3]. Second, the cumulative blood-pressure signal seen in Phase 2 intranasal studies scaled with dosing frequency, not peak plasma concentration, which supported a cap-based rather than titration-based dosing strategy [1,2].

Tolerance and desensitization have not been clearly documented in clinical trials of the subcutaneous 1.75 mg dose, but the monthly dosing cap (eight doses per 30 days) effectively precludes the exposure levels at which receptor-level desensitization would be expected to manifest. Long-term safety data beyond 52 weeks of on-demand use are limited, and the Vyleesi label explicitly advises reassessment of benefit after 8 weeks of use with discontinuation if no improvement in HSDD symptoms is documented.

For research-setting use of compounded or research-chemical product, published community self-report protocols describe 4-to-8-week observation periods with tracking of blood pressure before and after dosing, reflecting the cardiovascular signal identified in Phase 2 intranasal studies [2]. No peer-reviewed guidance endorses continuous daily dosing, and the clinical development program explicitly rejected that pattern.

PT-141 Side Effects and Safety Profile

In short: nausea hits roughly 40% of users, transient blood-pressure bumps are predictable, and focal hyperpigmentation is the reason for the 8-dose monthly cap.

In the pooled RECONNECT dataset of more than 600 bremelanotide-exposed women, the most frequent treatment-emergent adverse events were nausea (40%), flushing (20%), injection-site reactions (13%), headache (11%), and vomiting (5%) [4]. Nausea was typically transient, peaked within two hours of dosing, and led to discontinuation in approximately 8% of participants. Focal hyperpigmentation of the face, breasts, and gums was observed in 1% of subjects and was more common with more than eight doses per month, which is why the FDA label caps monthly use at eight doses [1].

Transient increases in systolic blood pressure of approximately 6 mm Hg and in diastolic blood pressure of approximately 3 mm Hg, peaking 2–4 hours after administration, were observed in clinical pharmacology studies. Because of this, the label contraindicates use in patients with uncontrolled hypertension or known cardiovascular disease [1,2]. A lesser, clinically insignificant decrease in heart rate has also been described.

Drug interactions include reduced oral naltrexone absorption (bremelanotide slows gastric emptying) and potential additive effects with other MC4R-active drugs such as setmelanotide. The label advises avoiding bremelanotide within 24 hours of a dose of oral naltrexone used for alcohol or opioid use disorder.

Bremelanotide is not recommended in pregnancy. Preclinical reproductive toxicity studies did not identify major teratogenic signals, but human data are absent [1]. Contraindications also include known hypersensitivity to bremelanotide or any of the excipients. The prescribing information also advises against use in women with cardiovascular risk factors that cannot be medically optimized, including uncontrolled hypertension, recent myocardial infarction, or stroke within six months.

Off-label male use, particularly in research-chemical settings, has generated case-report literature describing prolonged erections, persistent flushing, and nausea severe enough to limit repeat dosing [6]. The absence of any controlled trial of the 1.75 mg subcutaneous dose in men means the approved safety data cannot be extrapolated to male populations with confidence. The FDA has not approved bremelanotide for any male indication, and the Vyleesi label is restricted to premenopausal women with acquired, generalized HSDD.

PT-141 Vendor Ratings: Who Publishes Lab Data at ≥99% Purity?

Which PT-141 vendors publish lab data ≥99% purity?

TriedRx compiles publicly available third-party lab reports, transparency disclosures, and reputation signals for vendors selling bremelanotide under PT-141 and related labeling. Data points include COA cadence, lab accreditation, pharmacist/medical-director disclosure, and regulatory-action history. We gather the quality data. We grade the vendors. We publish the rankings — including what's missing. No vendor payments. No sponsored placements.

See all vendors reviewed for PT-141 → /brands?peptide=pt-141

Related: PT-141 Research Profile and Vendor Rankings

For the full research background on PT-141 — including melanocortin receptor pharmacology, clinical trial outcomes in HSDD, a summary of off-label male sexual-health use, and the TriedRx vendor rating summary — see the TriedRx PT-141 peptide profile. The profile also covers the distinction between bremelanotide and its structural precursor melanotan-2, the regulatory history of the Vyleesi approval, and current prescribing availability in the United States.

References

1. U.S. Food and Drug Administration. Vyleesi (bremelanotide injection) prescribing information. Reference ID 4454525, June 2019. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/210557s000lbl.pdf
2. Diamond LE, Earle DC, Rosen RC, Willett MS, Molinoff PB. Double-blind, placebo-controlled evaluation of the safety, pharmacokinetic properties and pharmacodynamic effects of intranasal PT-141, a melanocortin receptor agonist, in healthy males and patients with mild-to-moderate erectile dysfunction. Int J Impot Res. 2004;16(1):51-59. PMID: 15082798.
3. King SH, Mayorov AV, Balse-Srinivasan P, Hruby VJ, Vanderah TW, Wessells H. Melanocortin receptors, melanotropic peptides and penile erection. Curr Top Med Chem. 2007;7(11):1098-1106. PMID: 17912485.
4. Kingsberg SA, Clayton AH, Portman D, Williams LA, Krop J, Jordan R, Lucas J, Simon JA. Bremelanotide for the treatment of hypoactive sexual desire disorder: two randomized phase 3 trials. Obstet Gynecol. 2019;134(5):899-908. PMID: 31599840. DOI: 10.1097/AOG.0000000000003500.
5. Clayton AH, Althof SE, Kingsberg S, DeRogatis LR, Kroll R, Goldstein I, Kaminetsky J, Spana C, Lucas J, Jordan R, Portman DJ. Bremelanotide for female sexual dysfunctions in premenopausal women: a randomized, placebo-controlled dose-finding trial. Womens Health (Lond). 2016;12(3):325-337. PMID: 27253528.
6. Safarinejad MR, Hosseini SY. Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo-controlled study. J Urol. 2008;179(3):1066-1071. PMID: 18206941.
7. Molinoff PB, Shadiack AM, Earle D, Diamond LE, Quon CY. PT-141: a melanocortin agonist for the treatment of sexual dysfunction. Ann N Y Acad Sci. 2003;994:96-102. PMID: 12851303.
8. Simon JA, Kingsberg SA, Portman D, Williams LA, Krop J, Jordan R, Lucas J, Clayton AH. Long-term safety and efficacy of bremelanotide for hypoactive sexual desire disorder. Obstet Gynecol. 2019;134(5):909-917. PMID: 31599847.