Side-by-side · Research reference

HexarelinvsPT-141

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

APhase 1Reviewed19/45 cited

BFDA-ApprovedReviewed13/41 cited

Hexarelin

Hexapeptide GHRP · Cardio-tropic

100–200 mcgPer doseSmith 1996

Phase 1Evidence levelGhigo 1997

~70 minHalf-lifeSemenistaya 2010

SQ · Multiple sites · 1–3×/day

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

Hexarelin

PT-141

Primary target

Ghrelin receptor (GHS-R1a) + cardiac CD36Smith 1996 Ghigo 1997

Melanocortin-4 receptor (MC4R) in hypothalamusSimerly 2023 VYLEESI (bremelanotide injecti 2019

Pathway

GHS-R1a → Gαq → Ca²⁺ → GH release. CD36 engagement → direct cardio-tropic actionGhigo 1997

MC4R agonism in paraventricular nucleus → autonomic + neuroendocrine sexual arousal pathwaysSimerly 2023

Downstream effect

Strong GH pulse + IGF-1 elevation; cardio-protective effects in animal MI modelsGhigo 1997

Increased sexual desire and arousal; central rather than peripheral mechanismClayton 2015

Feedback intact?

Yes initially; tachyphylaxis with chronic useGhigo 1997

—

Origin

Synthetic hexapeptide His-D-2-Methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂Smith 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

Hexarelin

PT-141

Standard dose

100–200 mcg per injectionSmith 1996

1.75 mg SQVYLEESI (bremelanotide injecti 2019

Single dose ≥45 min before anticipated sexual activity. Max 1 dose / 24 hr.

Frequency

1–2× per day max (tachyphylaxis with chronic 3× daily)

PRN, max 8 doses / month

Lower / starter dose

50 mcg per dose

1 mg (off-label)

Evidence basis

Phase 1 / Phase 2 trialsSmith 1996 Ghigo 1997

FDA-approved (HSDD pre-menopausal women)VYLEESI (bremelanotide injecti 2019 Clayton 2015

Duration

4–8 weeks on / 4–8 weeks off (tachyphylaxis mitigation)

PRN; reassess if no benefit after 8 doses

Reconstitution

Bacteriostatic water

Pre-filled commercial pen (Vyleesi). Research vial: bacteriostatic water.

Timing

Pre-sleep + fasted preferred

≥45 min before sexual activity

Half-life

~70 minSemenistaya 2010

~2.7 hrVYLEESI (bremelanotide injecti 2019

04Side Effects & Safety

Parameter

Hexarelin

PT-141

Cortisol elevation

Modest at high dosesGhigo 1997

—

Prolactin elevation

Modest at high dosesGhigo 1997

—

Hunger

Strong appetite increase via ghrelin agonism

—

Tachyphylaxis

Receptor desensitisation with chronic dosingGhigo 1997

—

Cardiac effects

Direct cardio-tropic; potential benefit in MI but unstudied in humansGhigo 1997

—

IGF-1 elevation

Strong; monitor with chronic high-dose use

—

Cancer risk

Contraindicated in active malignancy (GH/IGF-1 axis)

—

Pregnancy / OB

Avoid

Contraindicated

Nausea

—

Common (~40%); often transientVYLEESI (bremelanotide injecti 2019

Flushing

—

Common, transient

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

Hexarelin

·Active malignancy
·Pregnancy / breastfeeding
·Disrupted hypothalamic-pituitary axis

PT-141

·Uncontrolled hypertension
·Known cardiovascular disease (caution)
·Pregnancy

Relative Contraindications

Hexarelin

·Untreated diabetes
·Severe hyperprolactinemia

PT-141

·Pre-existing hyperpigmentation disorders
·MC4R-pathway-dependent psychiatric conditions

05Administration Protocol

Parameter

Hexarelin

PT-141

1. Reconstitution

Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL = 250 mcg per 0.1 mL.

Vyleesi: pre-filled auto-injector. Research vial: 2 mL bacteriostatic water per 10 mg → 5 mg/mL.

2. Injection site

SQ — abdomen or thigh. Rotate sites.

SQ — abdomen or thigh.

3. Timing

Pre-sleep + fasted preferred. Cycle on/off to avoid tachyphylaxis.

≥45 min before sexual activity for peak effect. Effect persists ~6–8 h.

4. Storage

Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.

Vyleesi: room temp ≤30 °C. Research vial: refrigerate after reconstitution.

5. Needle

29–31G, 4–8 mm insulin syringe.

Auto-injector (Vyleesi) or 29–31G, 4–8 mm insulin syringe.

06Stack Synergy

Hexarelin

+ CJC-1295 (no DAC)

Strong

View CJC-1295 (no DAC) →

Hexarelin (GHRP) + CJC-1295-no-DAC (GHRH analogue) is the higher-amplitude variant of the standard GHRH+GHRP stack. Hexarelin produces a stronger pulse than ipamorelin but with cortisol + prolactin signal — choose this stack for maximum GH amplitude when side-effect tolerance is acceptable. Cycle aggressively.

Hexarelin: 100 mcg SQ · pre-sleep
CJC-1295 (no DAC): 100 mcg SQ · same injection
Primary benefit: Maximum GH pulse amplitude (with side-effect signal)

Smith 1996 Teichman 2006

PT-141

— no documented stacks