MK-2866 vs Ondansetron
Moderate Research vs FDA Approved
avoid Mechanism-based · 64% Both MK-2866 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-2866 Ondansetron
Weight 389.33 Da 293.36 Da
Half-life ~24 hours ~4 hours
Type Non-steroidal selective androgen receptor modulator (C19H14F3N3O3) Carbazole derivative (C18H19N3O)
Key Benefits
MK-2866
01 Increases lean body mass in a dose-dependent manner with clinical trial support
02 Preserves muscle mass during caloric deficit or catabolic conditions
03 Selective tissue activity reduces androgenic side effects compared to anabolic steroids
04 Oral bioavailability eliminates the need for injections
05 Does not aromatize to estrogen, avoiding gynecomastia and water retention
06 Improves physical function and stair-climbing power in clinical populations
07 Long 24-hour half-life allows convenient once-daily dosing
08 Mild side effect profile at commonly studied doses
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-2866
Mild testosterone suppression (dose-dependent, typically 10-30% reduction at 25 mg)
HDL cholesterol reduction (10-20% suppression observed in clinical trials)
Headaches, particularly during the first 1-2 weeks
Mild back pain or muscle cramps
Transient fatigue toward the end of longer cycles
Slight reduction in libido at higher doses or extended cycle lengths
Ondansetron
Headache (most frequently reported side effect)
Constipation (5-HT3 blockade reduces gut motility)
Fatigue or dizziness
Dry mouth
Contraindications
Active liver disease or significantly elevated liver enzymes
Hormone-sensitive cancers (breast, prostate) without oncologist clearance
Pregnancy or breastfeeding (potential endocrine disruption to fetus/infant)
Individuals under 21 years of age (risk of premature HPTA disruption during development)
Concurrent use of hepatotoxic medications without liver function monitoring
Known hypersensitivity to MK-2866 or any formulation excipients
Competitive athletes subject to WADA or USADA anti-doping testing
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-2866 Ondansetron
Status Moderate Research FDA Approved
References 5 studies 4 studies
FDA Approved No Yes
This comparison is for educational and research purposes only. Consult a healthcare professional before use.