MK-677 vs Semax
Well Studied vs Well Studied
monitor Mechanism-based · 51% Both MK-677 and Semax can raise blood pressure. Monitor BP regularly and consider adding cardiovascular support (cardarine, telmisartan, or similar).
Molecular Data
MK-677 Semax
Weight 624.77 Da 813.93 Da
Half-life ~24 hours 0.5-2 hours
Chain — 7 amino acids
Type Non-peptide ghrelin receptor agonist ACTH(4-10) synthetic analog
Key Benefits
MK-677
01 97% increase in 24-hour growth hormone secretion
02 40-72% elevation in IGF-1 levels
03 Enhanced sleep quality with improved REM patterns
04 Preferential lean tissue gains of 1.1-2.7kg over 8-12 months
05 15% basal metabolic rate increase within 2 weeks
06 Oral administration (no injections required)
Semax
01 Rapid brain delivery via intranasal route
02 Rapidly increases BDNF levels
03 Extensive clinical research in Russia
04 Easy self-administration
05 Modulates dopamine and serotonin systems
06 Neuroprotective effects
Dosing Protocols
MK-677
Start 12.5mg daily, increase to 25mg based on tolerance / Once daily, preferably at bedtime on empty stomach
Semax
300-600mcg per dose (up to 1000mcg for intensive use) / 1-2x daily (morning recommended for cognitive boost)
Research protocol 500-750mcg 1x daily
Intensive protocol 750-1000mcg 1-2x daily
Side Effects
MK-677
Appetite stimulation (>50% of users)
Water retention (30-40%)
Lethargy (20-30%)
Fasting glucose elevation (5-15mg/dL)
Note on testosterone suppression: at doses up to 20 mg daily, MK-677 is unlikely to cause significant testosterone suppression on its own. Above 20 mg daily, the likelihood of suppression and other side effects (insulin resistance, water retention, lethargy) increases. The case report documenting 85.7% testosterone suppression involved co-administration with LGD-4033, a SARM known to be profoundly suppressive, making the SARM the likely primary driver of that suppression.
Semax
Mild nasal discomfort (nasal route)
Possible nasal sensation upon administration
Contraindications
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Pregnancy or breastfeeding
Known peptide allergies
Do not exceed 4-week continuous use without medical supervision
Research Evidence
MK-677 Semax
Status Well Studied Well Studied
References 7 studies 5 studies
Latest July 2024 2025
FDA Approved No No
This comparison is for educational and research purposes only. Consult a healthcare professional before use.