Side-by-side · Research reference
PT-141vsTB-500
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
AFDA-ApprovedReviewed13/41 cited
BPhase 2Reviewed8/46 cited
PT-141
MC4R Agonist · FDA-Approved (HSDD)
SQ · Abdomen / thigh · ≥45 min before sex
TB-500
Thymosin β4 fragment · Healing
SQ or IM · Multiple sites · 2–3×/week
01Mechanism of Action
Parameter
PT-141
TB-500
Primary target
Melanocortin-4 receptor (MC4R) in hypothalamusSimerly 2023VYLEESI (bremelanotide injecti 2019
G-actin (sequestering) + cell-surface integrinsGoldstein 2012
Pathway
MC4R agonism in paraventricular nucleus → autonomic + neuroendocrine sexual arousal pathwaysSimerly 2023
Actin remodelling → cell migration; integrin-linked signaling → angiogenesis; anti-inflammatory cytokine modulationGoldstein 2012Malinda 1999
Downstream effect
Increased sexual desire and arousal; central rather than peripheral mechanismClayton 2015
Accelerated wound healing, endothelial migration, hair follicle regeneration, cardiac repair (preclinical)Goldstein 2012
Feedback intact?
—
Endogenous protein at baseline; supplementation amplifies
Origin
Cyclic 7-AA peptide derived from α-MSH (agonist Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-OH cyclic)VYLEESI (bremelanotide injecti 2019
17-AA active fragment of endogenous 43-AA thymosin β4 (TMSB4X gene)Goldstein 2012
Antibody development
—
—
02Dosage Protocols
Parameter
PT-141
TB-500
Standard dose
1.75 mg SQVYLEESI (bremelanotide injecti 2019
Single dose ≥45 min before anticipated sexual activity. Max 1 dose / 24 hr.
2 mg per injectionGoldstein 2012
Anecdotal community range; clinical Phase 2 trials used 70–840 mcg/kg IV.
Frequency
PRN, max 8 doses / month
2× per week (loading); then 1× per week (maintenance)
Lower / starter dose
1 mg (off-label)
1 mg per injection
Evidence basis
FDA-approved (HSDD pre-menopausal women)VYLEESI (bremelanotide injecti 2019Clayton 2015
Animal-strong + Phase 2 dermal/ocular trialsGoldstein 2012
Duration
PRN; reassess if no benefit after 8 doses
4–8 weeks loading; longer maintenance for chronic injury
Reconstitution
Pre-filled commercial pen (Vyleesi). Research vial: bacteriostatic water.
Bacteriostatic water, 1–2 mL per 5 mg vial
Timing
≥45 min before sexual activity
Evening or pre-rest preferred (anecdotal)
04Side Effects & Safety
Parameter
PT-141
TB-500
Flushing
Common, transient
—
Injection site reaction
Erythema, mild pain
Mild erythema, transient 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
—
Pregnancy / OB
Contraindicated
Avoid
Cardiovascular disease
Use caution; transient BP rise
—
GI symptoms
—
Rare nausea (anecdotal)
Cancer risk
—
Theoretical via angiogenesis pathway
Lethargy / fatigue
—
Reported anecdotally during loading phase
Antibody formation
—
No data (no long-term human trials)
Long-term safety
—
Unknown beyond Phase 2
Absolute Contraindications
PT-141
- ·Uncontrolled hypertension
- ·Known cardiovascular disease (caution)
- ·Pregnancy
TB-500
- ·Active malignancy (theoretical angiogenesis concern)
- ·Pregnancy / breastfeeding
Relative Contraindications
PT-141
- ·Pre-existing hyperpigmentation disorders
- ·MC4R-pathway-dependent psychiatric conditions
TB-500
- ·Cancer history
- ·Concurrent VEGF inhibitor therapy
05Administration Protocol
Parameter
PT-141
TB-500
1. Reconstitution
Vyleesi: pre-filled auto-injector. Research vial: 2 mL bacteriostatic water per 10 mg → 5 mg/mL.
Add 1–2 mL bacteriostatic water to 5 mg vial → 2.5–5 mg/mL. Roll gently.
2. Injection site
SQ — abdomen or thigh.
SQ near injury site (preferred), or systemic SQ (abdomen). Rotate sites.
3. Timing
≥45 min before sexual activity for peak effect. Effect persists ~6–8 h.
Evening or pre-sleep is most common anecdotal timing.
4. Storage
Vyleesi: room temp ≤30 °C. Research vial: refrigerate after reconstitution.
Lyophilised: room temp, light-protected. Reconstituted: refrigerate, ≤30 days.
5. Needle
Auto-injector (Vyleesi) or 29–31G, 4–8 mm insulin syringe.
27–31G, 4–8 mm insulin syringe.
06Stack Synergy
PT-141
— no documented stacks
TB-500
+ BPC-157
StrongTB-500 and BPC-157 cover complementary halves of tissue repair: BPC-157 upregulates VEGFR2-driven angiogenesis and fibroblast outgrowth; TB-500 sequesters G-actin to enable endothelial / epithelial migration. The anecdotal canonical "healing stack" — pairs especially well for tendon and ligament injuries.
- TB-500
- 2 mg SQ · 2× per week
- BPC-157
- 250–500 mcg SQ · daily
- Primary benefit
- Combined angiogenesis + cell migration for tendon/ligament/muscle repair