Side-by-side · Research reference
Melanotan-IIvsThymosin α-1
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 1Reviewed9/43 cited
BPhase 3Reviewed8/39 cited
Melanotan-II
MC1R + MC4R agonist · Tanning + sexual response
SQ · Abdomen · Loading 5–7 days, then maintenance
Thymosin α-1
Immune modulator · Approved (some countries)
SQ · 2× weekly · 6+ months for chronic indications
01Mechanism of Action
Parameter
Melanotan-II
Thymosin α-1
Primary target
MC1R (skin) + MC3R + MC4R (CNS sexual / appetite)Dorr 1996
Toll-like receptor 9 (TLR9) + T-cell maturation pathwayCamerini 2001
Pathway
MC1R agonism → melanocyte tyrosinase → eumelanin synthesis. MC4R → autonomic sexual arousal centresDorr 1996Simerly 2023
TLR9 activation → ↑ IFN-α + IL-2 + IFN-γ → enhanced T-cell function + dendritic cell maturationIyer 2007
Downstream effect
Skin darkening, photo-protection, increased sexual desire / spontaneous erectionDorr 1996
Restored T-cell function, improved viral clearance, anti-tumour adjuvant effectsIyer 2007
Feedback intact?
—
—
Origin
Cyclic 7-AA modified α-MSH analog; designed at University of ArizonaDorr 1996
Synthetic 28-AA peptide identical to natural Tα-1 isolated from thymus extractCamerini 2001
Antibody development
—
—
02Dosage Protocols
Parameter
Melanotan-II
Thymosin α-1
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
2× weekly (Mon/Thu typical)
Lower / starter dose
0.1 mg / day
Conservative starter — assess tolerability for nausea.
0.8 mg per injection
Duration
8–12 weeks per cycle
6–12 months for chronic indications
Reconstitution
Bacteriostatic water; protect from light
Sterile water for injection per vial label
Timing
Evening preferred (24h tan-development cycle)
No specific time
Half-life
~1 hour plasma; effects on melanocytes persist days
~2 hours plasma; tissue effect days
04Side Effects & Safety
Parameter
Melanotan-II
Thymosin α-1
Nausea
Common, especially loading phase
—
Flushing
Common transient
—
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
Avoid
Injection site reaction
—
Erythema, mild discomfort
GI symptoms
—
Rare nausea
Fatigue
—
Common during initial weeks
Fever / flu-like
—
Mild interferon-like response possible
Autoimmune
—
Theoretical risk; caution in active autoimmune disease
Cancer risk
—
No signal — used as adjuvant in oncology
Absolute Contraindications
Melanotan-II
- ·History of melanoma or atypical mole syndrome
- ·Pregnancy / breastfeeding
- ·Active uncontrolled hypertension
Thymosin α-1
- ·Pregnancy / breastfeeding
- ·Hypersensitivity to peptide
- ·Concurrent immunosuppressant therapy (transplant patients)
Relative Contraindications
Melanotan-II
- ·Significant freckling / dysplastic nevus
- ·Personal or family melanoma history
Thymosin α-1
- ·Active autoimmune disease
- ·Severe immunocompromised state without supervision
05Administration Protocol
Parameter
Melanotan-II
Thymosin α-1
1. Reconstitution
Add 2 mL bacteriostatic water to 10 mg vial → 5 mg/mL = 500 mcg per 0.1 mL. Light-protected.
Add 1 mL sterile water per 1.6 mg vial → 1.6 mg/mL.
2. Injection site
SQ — abdomen. Rotate sites.
SQ — abdomen, thigh, or upper arm. Rotate sites.
3. Timing
Evening preferred. UV exposure (sunlight or tanning bed) helps develop tan.
2× weekly, e.g. Monday + Thursday.
4. Storage
Lyophilised: refrigerate, light-protected. Reconstituted: refrigerate ≤30 days.
Lyophilised: refrigerate. Reconstituted: refrigerate, use within 24 h.
5. Needle
29–31G insulin syringe.
27–31G, 4–8 mm insulin syringe.