01 — Identity

Name & Classification

PT-141, generically known as Bremelanotide, is a synthetic cyclic heptapeptide analogue of alpha-melanocyte stimulating hormone (α-MSH). Its chemical designation is cyclo-(Nle⁴-Asp⁵-His⁶-D-Phe⁷-Arg⁸-Trp⁹-Lys¹⁰)-α-MSH(4-10).

It is an agonist of melanocortin receptors MC3R and MC4R in the central nervous system. Critically, unlike PDE5 inhibitors (Viagra, Cialis), PT-141 acts via the brain and nervous system — not the vasculature — making it effective in both men and women and in cases where vascular ED treatments have failed. It received FDA approval in 2019 under the brand name Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women.

02 — Origin

When It Was Developed

1960s–80s

Alpha-MSH studied for pigmentation effects. Role of melanocortin receptors in sexual behavior observed incidentally in research animals receiving synthetic MSH analogues.

Early 1990s

University of Arizona researchers Victor Hruby and Mac Hadley studying the tanning peptide Melanotan-II noted spontaneous erections in male subjects — leading to isolation of the sexual arousal mechanism.

2000

PT-141 derived as a metabolite of Melanotan-II (removing the tanning effect). Licensed to Palatin Technologies for development as a sexual dysfunction drug.

2000s

Phase 1/2 trials showed efficacy in erectile dysfunction and female sexual arousal disorder. Early intranasal formulations caused blood pressure increases, prompting shift to subcutaneous delivery.

2019

FDA approved as Vyleesi (bremelanotide) for HSDD in premenopausal women — the first non-hormonal, on-demand treatment for female sexual dysfunction ever approved.

03 — Research History

Research Background

PT-141 emerged from a serendipitous observation: subjects in a tanning peptide study were experiencing erections. This led to focused research on melanocortin receptor subtypes MC3R and MC4R in the hypothalamus and limbic system — areas governing sexual motivation and arousal.

Unlike PDE5 inhibitors which work peripherally by increasing blood flow, PT-141 works centrally — activating dopaminergic pathways in the hypothalamus to generate genuine sexual desire and arousal, not just a mechanical response. This makes it particularly valuable for desire disorders and cases where physical arousal is possible but psychological/neurological desire is impaired.

Phase 3 data for HSDD showed statistically significant improvements in satisfying sexual events and desire scores versus placebo, leading to FDA approval. Off-label use in men for ED — particularly cases unresponsive to PDE5 inhibitors — has grown substantially in the research/wellness space.

04 — Key Benefits

Proposed Benefits

FDA-approved for HSDD in premenopausal women (Vyleesi)

Increases sexual desire and motivation via central CNS action

Effective in both men and women — unique among sexual function drugs

Works in cases where PDE5 inhibitors (Viagra/Cialis) have failed

On-demand dosing — taken 45 min before activity

Does not require sexual stimulation to initiate response

Activates dopaminergic pathways — addresses psychological desire deficit

Effects last 6–12 hours with single dose

05 — Reconstitution

10 mg Vial + 300 Units BAC Water

33.3 mcg

per unit drawn on insulin syringe

10,000

mcg total

0.3 mL

total volume

4–6 wk

shelf life (fridge)

🧊

RECONSTITUTED SHELF LIFE

28 days after mixing

Melanocortin analog. 28-day window.

            Storage: 2–8°C (fridge) · Protected from light · Do NOT freeze

            Preload syringes/cartridges to minimize vial disturbance

Store refrigerated at 36–46°F / 2–8°C after reconstitution. PT-141 is relatively stable in solution. The FDA-approved Vyleesi auto-injector delivers 1.75 mg per dose — research formulations typically aim for the same range. Do not freeze reconstituted peptide.

06 — Dosage

Dosage Reference

Dose	Units to Draw	Context
500 mcg (0.5 mg)	~15 u	LOW / INTRO
1,000 mcg (1.0 mg)	~30 u	COMMON
1,750 mcg (1.75 mg)	~52.5 u	FDA DOSE (Vyleesi)
2,000 mcg (2.0 mg)	~60 u	STANDARD MAX

PT-141 is an on-demand peptide — it is NOT used daily. The FDA-approved dose is 1.75 mg SC 45 minutes before activity, no more than once every 24 hours and no more than 8 times per month. Nausea (the primary side effect) is dose-dependent — start at 500 mcg–1 mg to assess tolerance. Flushing and transient blood pressure increase are common at higher doses.

07 — Monitoring

Biomarkers, Lab Tests & Ranges

PT-141 acts centrally on the CNS. Key monitoring focuses on hormonal status, cardiovascular safety (blood pressure), and the underlying drivers of sexual dysfunction.

▸ Hormonal Panel

Biomarker	Lab Test	Clinical Range	Optimal Range
Total Testosterone	Serum Total Testosterone	CLINICALM: 264–916 ng/dL / F: 15–70 ng/dL	OPTIMALM: 600–900 ng/dL / F: 40–60 ng/dL
Free Testosterone	Free Testosterone (direct or calculated)	CLINICALM: 9–30 ng/dL / F: 0.3–1.9 ng/dL	OPTIMALM: upper quartile for age / F: mid-range
Estradiol (E2)	Serum Estradiol (sensitive assay)	CLINICALM: 10–40 pg/mL / F: cycle-dependent	OPTIMALM: 20–30 pg/mL / F: 50–150 (follicular)
LH / FSH	Serum LH & FSH	CLINICALLH: 1.7–8.6 / FSH: 1.5–12.4 mIU/mL	OPTIMALMid-range; LH 3–7 / FSH 2–8 mIU/mL
Prolactin	Serum Prolactin	CLINICALM: 2–18 / F: 2–29 ng/mL	OPTIMALM: 5–12 / F: 5–18 ng/mL
DHEA-S	Serum DHEA-Sulfate	CLINICALAge/sex dependent (wide range)	OPTIMALUpper 25th percentile for age/sex

▸ Cardiovascular Safety

Biomarker	Lab Test	Clinical Range	Optimal Range
Blood Pressure Key safety parameter	Office / Home BP Monitoring	CLINICAL<130/80 mmHg	OPTIMAL110–120 / 70–80 mmHg
hsCRP	High-sensitivity CRP	CLINICAL<3.0 mg/L	OPTIMAL<0.5 mg/L

▸ Safety Panel

Biomarker	Lab Test	Clinical Range	Optimal Range
AST / ALT	CMP	CLINICALAST 10–40 / ALT 7–56 U/L	OPTIMALAST <26 / ALT <26 U/L
CBC	Complete Blood Count	CLINICALStandard ranges	OPTIMALMid-range; WBC 4.5–6.0

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⚠ PT-141 is FDA-approved as Vyleesi for HSDD. Contraindicated in cardiovascular disease, uncontrolled hypertension, and with certain BP medications. Nausea occurs in ~40% at the 1.75 mg dose — starting at 0.5–1 mg significantly reduces this. Not for daily use.

08 — Cycle Protocol

Cycle Length, Frequency & Timing

▸ Usage Pattern

FDA-APPROVED USE

On-Demand

PT-141 is not a daily peptide. It is taken as-needed, 45 minutes before sexual activity, max once per 24 hours, no more than 8 uses per month per FDA labeling.

RESEARCH / OFF-LABEL

As-Needed

No traditional "cycle" applies. Use as-needed with spacing to avoid tachyphylaxis (reduced response with repeated use). Most practitioners recommend minimum 3 days between doses for consistent response.

Tachyphylaxis warning: Frequent daily use reduces receptor response. The FDA max of 8×/month exists partly for this reason. For best efficacy, use PT-141 sparingly and with adequate spacing. Nausea can be reduced by staying hydrated, taking slowly, and dosing at the lower end of the range.

▸ Timing Protocol

Variable	Recommendation	Why
When to inject	45–60 min before activity	Peak CNS effect occurs at 45–70 minutes post-injection. Effects persist 6–12 hours. The FDA label specifies at least 45 minutes prior.
Fasted vs Fed	~ Either acceptable	Food does not significantly affect efficacy but a heavy meal may increase nausea risk. Light meal or fasted state preferred for tolerability.
Injection site	SC — abdomen or thigh	Subcutaneous injection in the abdomen or thigh as per the Vyleesi auto-injector labeling. Rotate sites to reduce local reactions.
Minimum spacing	72 hrs between doses	3 days between uses preserves receptor sensitivity and minimizes tachyphylaxis. FDA allows once per 24 hrs but 72 hrs is preferred for sustained efficacy.

PROTOCOL SUMMARY

On-Demand

DOSING STYLE

≤8×/mo

MAX FREQUENCY

45–60 min

BEFORE ACTIVITY

72 hrs

MIN SPACING

6–12 hrs

EFFECT DURATION