Naltrexone is an opioid receptor antagonist used at standard doses (50mg) to treat opioid and alcohol addiction, and at low doses (1.5-4.5mg, LDN) to modulate immune function and reduce inflammation through temporary blockade of opioid receptors, triggering compensatory upregulation of endorphins and opioid receptors.
Naltrexone competitively binds mu, delta, and kappa opioid receptors. At low doses (LDN), brief overnight blockade (4-6 hours) triggers a rebound increase in endorphin production and opioid receptor density during the day. This paradoxical effect enhances endogenous opioid tone, modulates immune cell function (particularly macrophages and T cells), reduces pro-inflammatory cytokine production (IL-6, TNF-Ξ±), and may activate Toll-like receptors on immune cells.
Low-dose naltrexone (LDN) is used off-label in cPNI for autoimmune conditions, chronic pain, fibromyalgia, multiple sclerosis, and inflammatory bowel disease. The immune-modulating effects occur through enhanced endorphin signaling and direct effects on immune cells. Must be taken at night to maximize rebound effect during active hours.
- Standard dose: 50mg for addiction treatment
- Low-dose range (LDN): 1.5-4.5mg for immune modulation
- Half-life: 4 hours (naltrexone), 13 hours (active metabolite 6-Ξ²-naltrexol)
- LDN timing: bedtime to allow rebound during daytime hours
- Increases endorphin production by 200-300% during rebound phase
- Upregulates opioid receptors by 40-60%
- Reduces IL-6 and TNF-Ξ± in clinical trials
- Contraindicated with opioid medications (blocks therapeutic effect)
- Takes 2-3 months for full immune-modulating benefits
- MOR β antagonizes mu opioid receptors to trigger rebound
- DOR β blocks delta opioid receptors
- KOR β antagonizes kappa opioid receptors
- Endorphins β increases endogenous endorphin production through rebound mechanism
- Beta-endorphin β specifically increases Ξ²-endorphin levels
- IL-6 β reduces pro-inflammatory IL-6 production
- TNF-Ξ± β decreases TNF-Ξ± levels in inflammatory conditions
- Macrophages β modulates macrophage function and polarization
- T cells β affects T cell activation and cytokine production
- TLR β may interact with Toll-like receptors on immune cells
- Autoimmune disease β used therapeutically in various autoimmune conditions
- Multiple Sclerosis β clinical evidence for benefit in MS
- Fibromyalgia β reduces pain and improves function in fibromyalgia
- Inflammatory bowel disease β shows promise in Crohn's disease and ulcerative colitis
- Chronic pain β paradoxically reduces pain through enhanced endorphin signaling
- Opioid tolerance β can help reverse tolerance in chronic opioid users
- Inflammation β broad anti-inflammatory effects through immune modulation
- Periaqueductal gray β endorphin rebound enhances descending pain inhibition from PAG
- Reward system β modulates dopamine-endorphin interactions in reward pathways
- Addiction β standard dose blocks rewarding effects of alcohol and opioids