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Specimen Atlas of Research Peptides30 plates · MIT
PeptidesDBan atlas
Side-by-side · Research reference

Melanotan-IIvsPT-141

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

APhase 1Reviewed9/43 cited
BFDA-ApprovedReviewed13/41 cited
Melanotan-II
MC1R + MC4R agonist · Tanning + sexual response
0.25–1.0 mgPer doseDorr 1996
Phase 1Evidence levelDorr 1996
~1 hrHalf-life
SQ · Abdomen · Loading 5–7 days, then maintenance
PT-141
MC4R Agonist · FDA-Approved (HSDD)
1.75 mgPer doseVYLEESI (bremelanotide injecti 2019
Pre-sexTimingVYLEESI (bremelanotide injecti 2019
~2.7 hrHalf-lifeVYLEESI (bremelanotide injecti 2019
SQ · Abdomen / thigh · ≥45 min before sex

01Mechanism of Action

Parameter
Melanotan-II
PT-141
Primary target
MC1R (skin) + MC3R + MC4R (CNS sexual / appetite)Dorr 1996
Melanocortin-4 receptor (MC4R) in hypothalamusSimerly 2023VYLEESI (bremelanotide injecti 2019
Pathway
MC1R agonism → melanocyte tyrosinase → eumelanin synthesis. MC4R → autonomic sexual arousal centresDorr 1996Simerly 2023
MC4R agonism in paraventricular nucleus → autonomic + neuroendocrine sexual arousal pathwaysSimerly 2023
Downstream effect
Skin darkening, photo-protection, increased sexual desire / spontaneous erectionDorr 1996
Increased sexual desire and arousal; central rather than peripheral mechanismClayton 2015
Feedback intact?
—
—
Origin
Cyclic 7-AA modified α-MSH analog; designed at University of ArizonaDorr 1996
Cyclic 7-AA peptide derived from α-MSH (agonist Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-OH cyclic)VYLEESI (bremelanotide injecti 2019
Antibody development
—
—

02Dosage Protocols

Parameter
Melanotan-II
PT-141
Loading phase
0.25–0.5 mg/day SQ × 5–7 daysDorr 1996
Builds up to visible tan.
—
Maintenance
0.5–1.0 mg 1–2×/week
After visible tan develops; supports with UV exposure.
—
Frequency
Daily during loading; 1–2× per week maintenance
PRN, max 8 doses / month
Lower / starter dose
0.1 mg / day
Conservative starter — assess tolerability for nausea.
1 mg (off-label)
Evidence basis
Phase 1 + anecdotalDorr 1996
FDA-approved (HSDD pre-menopausal women)VYLEESI (bremelanotide injecti 2019Clayton 2015
Duration
8–12 weeks per cycle
PRN; reassess if no benefit after 8 doses
Reconstitution
Bacteriostatic water; protect from light
Pre-filled commercial pen (Vyleesi). Research vial: bacteriostatic water.
Timing
Evening preferred (24h tan-development cycle)
≥45 min before sexual activity
Half-life
~1 hour plasma; effects on melanocytes persist days
~2.7 hrVYLEESI (bremelanotide injecti 2019
Standard dose
—
1.75 mg SQVYLEESI (bremelanotide injecti 2019
Single dose ≥45 min before anticipated sexual activity. Max 1 dose / 24 hr.

04Side Effects & Safety

Parameter
Melanotan-II
PT-141
Nausea
Common, especially loading phase
Common (~40%); often transientVYLEESI (bremelanotide injecti 2019
Flushing
Common transient
Common, transient
Spontaneous erection
Common in men — MC4R cross-effectDorr 1996
—
Increased mole / freckle pigmentation
Existing moles darken; new lesions possible
—
Melanoma risk
Theoretical concern — increased melanocyte activity; CAUTION in melanoma history
—
Appetite suppression
MC4R-mediated; mild
—
Pregnancy / OB
Contraindicated
Contraindicated
Injection site reaction
—
Erythema, mild pain
Headache
—
Common
Hyperpigmentation (focal)
—
Rare focal skin darkening; reversible after discontinuationVYLEESI (bremelanotide injecti 2019
Hypertension (transient)
—
Mean ↑6 mmHg systolic peaking ~4 h post-dose; resolves within 12 hVYLEESI (bremelanotide injecti 2019
Cardiovascular disease
—
Use caution; transient BP rise
Absolute Contraindications
Melanotan-II
  • ·History of melanoma or atypical mole syndrome
  • ·Pregnancy / breastfeeding
  • ·Active uncontrolled hypertension
PT-141
  • ·Uncontrolled hypertension
  • ·Known cardiovascular disease (caution)
  • ·Pregnancy
Relative Contraindications
Melanotan-II
  • ·Significant freckling / dysplastic nevus
  • ·Personal or family melanoma history
PT-141
  • ·Pre-existing hyperpigmentation disorders
  • ·MC4R-pathway-dependent psychiatric conditions

05Administration Protocol

Parameter
Melanotan-II
PT-141
1. Reconstitution
Add 2 mL bacteriostatic water to 10 mg vial → 5 mg/mL = 500 mcg per 0.1 mL. Light-protected.
Vyleesi: pre-filled auto-injector. Research vial: 2 mL bacteriostatic water per 10 mg → 5 mg/mL.
2. Injection site
SQ — abdomen. Rotate sites.
SQ — abdomen or thigh.
3. Timing
Evening preferred. UV exposure (sunlight or tanning bed) helps develop tan.
≥45 min before sexual activity for peak effect. Effect persists ~6–8 h.
4. Storage
Lyophilised: refrigerate, light-protected. Reconstituted: refrigerate ≤30 days.
Vyleesi: room temp ≤30 °C. Research vial: refrigerate after reconstitution.
5. Needle
29–31G insulin syringe.
Auto-injector (Vyleesi) or 29–31G, 4–8 mm insulin syringe.