MK-2866 vs Naltrexone
Moderate Research vs FDA Approved
avoid Mechanism-based · 64% Both MK-2866 and Naltrexone 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 Naltrexone
Weight 389.33 Da 341.40 Da
Half-life ~24 hours ~4 hours
Type Non-steroidal selective androgen receptor modulator (C19H14F3N3O3) Opioid antagonist (C20H23NO4)
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
Naltrexone
01 Broad anti-inflammatory and immunomodulatory effects via OGF-OGFr axis upregulation
02 Reduction in pro-inflammatory cytokines (TNF-alpha, IL-6, IL-12) through TLR4 antagonism
03 Compensatory upregulation of endogenous endorphins and enkephalins (200-300% increase)
04 Improved immune regulation and rebalancing of Th1/Th2/Th17 responses
05 Reduction in chronic pain through central and peripheral opioid system modulation
06 Potential improvement in mood, anhedonia, and overall well-being via endorphin enhancement
07 Extremely well-tolerated with minimal side effects at low doses
08 Low cost, especially as compounded LDN formulation
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
Naltrexone
Vivid dreams or unusually intense dreaming - the most frequently reported side effect, typically diminishes over 1-2 weeks
Initial sleep disruption or insomnia during the first week of treatment
Mild nausea, particularly during the first few days
Transient headache during dose initiation or titration
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
Current use of opioid medications or active opioid dependence (must be opioid-free 7-10 days minimum)
Acute hepatitis or severe hepatic impairment (primarily relevant at full dose)
Known hypersensitivity to naltrexone
Anticipated need for opioid pain medication (e.g., upcoming surgery - discontinue LDN 3-7 days prior)
Research Evidence
MK-2866 Naltrexone
Status Moderate Research FDA Approved
References 5 studies 5 studies
Latest — 2023
FDA Approved No Yes
This comparison is for educational and research purposes only. Consult a healthcare professional before use.