MK-677 vs Ondansetron
Well Studied vs FDA Approved
avoid Mechanism-based · 64% Both MK-677 and Ondansetron carry hepatotoxic risk. Combining hepatotoxic compounds significantly increases liver damage potential. If unavoidable, include liver support (TUDCA/NAC) and monitor ALT/AST frequently.
Molecular Data
MK-677 Ondansetron
Weight 624.77 Da 293.36 Da
Half-life ~24 hours ~4 hours
Type Non-peptide ghrelin receptor agonist Carbazole derivative (C18H19N3O)
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)
Ondansetron
01 Highly effective at controlling nausea and vomiting from a wide range of causes, including GLP-1 agonists, HCG, and nandrolone
02 Orally disintegrating tablet (ODT) dissolves on the tongue in seconds, ideal for use during active nausea when swallowing pills is difficult
03 Does not cause sedation, extrapyramidal symptoms, or prolactin elevation, unlike dopamine-blocking anti-emetics
04 Fast onset of action (15-30 minutes oral, near-immediate for ODT) with reliable 4-8 hour duration
05 Well-tolerated with a mild side effect profile at standard doses
06 Widely available as an inexpensive generic in multiple formulations
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.
Ondansetron
Headache (most frequently reported side effect)
Constipation (5-HT3 blockade reduces gut motility)
Fatigue or dizziness
Dry mouth
Contraindications
Heart disease or congestive heart failure
Diabetes or pre-diabetes
Active cancer
Severe cardiovascular disease
Pregnancy or breastfeeding
Known hypersensitivity to ondansetron or other 5-HT3 antagonists
Congenital long QT syndrome
Concurrent use of apomorphine (risk of severe hypotension and loss of consciousness)
Severe hepatic impairment (maximum dose should not exceed 8 mg/day)
Research Evidence
MK-677 Ondansetron
Status Well Studied FDA Approved
References 7 studies 4 studies
Latest July 2024 —
FDA Approved No Yes
This comparison is for educational and research purposes only. Consult a healthcare professional before use.