What is Low-Dose Naltrexone?

LDN is naltrexone at 1/10th to 1/50th the addiction treatment dose. At 1-4.5mg (vs 50mg), it briefly blocks opioid receptors, causing rebound endorphin production. Also modulates TLR4 immune signaling.

What conditions is LDN used for?

Off-label: autoimmune (MS, Crohn's, fibromyalgia, rheumatoid arthritis), chronic pain, cancer adjunct, Long COVID. Most research is off-label since LDN is FDA-approved only for addiction.

Does LDN require compounding?

Yes — standard naltrexone tablets are 50mg. For LDN (1-4.5mg), you need a compounding pharmacy to produce low-dose capsules or liquid. Not available at standard pharmacies.

Generally mild: vivid dreams, sleep disturbance in first week, mild GI upset. Many patients report increased energy and pain relief after initial adjustment period.

Brief receptor blockade (4-6 hours) causes upregulation of endogenous endorphins. Also modulates TLR4 (toll-like receptor 4) on immune cells, reducing inflammatory signaling.

Naltrexone is FDA-approved for addiction treatment at 50mg. LDN at 1-4.5mg is OFF-LABEL — not FDA-approved for any condition. Requires compounding pharmacy.

Off-Label Use • 90% Research

Low-Dose Naltrexone: Immune Modulation Research

By MeetPeptide Research Team

Last updated: March 2026

Opioid antagonist at 1/10th to 1/50th the addiction dose. Brief receptor blockade causes rebound endorphin increase. Modulates TLR4 for anti-inflammatory effects.

LDN
Dose Range

Off-Label
Research

Compounding
Required

Background

What Is LDN?

Low-Dose Naltrexone uses naltrexone at micro-doses (1-4.5mg vs 50mg for addiction treatment). The low dose creates a brief receptor blockade followed by upregulation of the body's own opioid system.

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Endorphin Upregulation

Brief opioid receptor blockade (4-6 hours) triggers compensatory increase in endogenous endorphins. Patients report improved mood, energy, and pain relief.

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TLR4 Modulation

Naltrexone at low doses modulates toll-like receptor 4 (TLR4) on microglia and immune cells. This reduces pro-inflammatory cytokine release.

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Autoimmune Modulation

LDN appears to modulate immune function in autoimmune conditions — reducing disease activity in MS, Crohn's, fibromyalgia. Mechanism still being elucidated.

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Compounding Required

Standard naltrexone is 50mg tablets. LDN doses (1-4.5mg) require compounding pharmacy. Not available at regular pharmacies.

Research

What the Research Shows

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Context: ~90% of LDN research is off-label. Naltrexone FDA-approved for addiction (50mg). LDN research is mostly case series, small trials, and patient-reported outcomes. Growing interest from functional medicine.

Multiple Sclerosis — Disability Scores

Multiple small studies show reduced fatigue, improved quality of life

Positive

Crohn's Disease — Remission Rates

Pilot study: 67% achieved remission vs 0% placebo

Promising

Fibromyalgia — Pain Scores

Small RCT: significant reduction in pain, improved function

Positive

Long COVID — Clinical Trials

Ongoing trials for fatigue, brain fog, post-exertional malaise

Pending

Protocol

Dosing & Administration

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Standard LDN Protocol

Start: 0.5mg-1mg at bedtime
Titrate up over 2-3 weeks
Target: 1.5-4.5mg nightly
Take at bedtime (blocks receptors during sleep)

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Timing Guidelines

Take 1-2 hours before bed
Side effects (vivid dreams) usually resolve in first week
Some prefer morning if dreams persist
Consistency more important than exact time

Bottom Line

Key Takeaways

✅ What We Know

Brief opioid receptor blockade upregulates endogenous endorphins
TLR4 modulation reduces inflammatory signaling
Generally well-tolerated with mild side effects
Compounding pharmacy produces low-dose capsules
Growing off-label use in autoimmune conditions

⚠️ What We Don't Know

LDN is OFF-LABEL — not FDA-approved for any condition
Most studies are small or observational
Optimal dosing still being refined
Long-term effects unclear
Requires compounding pharmacy

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⚠️ Disclaimer

LDN is OFF-LABEL — naltrexone is FDA-approved for addiction treatment (50mg), but LDN (1-4.5mg) is not approved for any medical condition. Requires compounding pharmacy. This is not medical advice. Always consult a healthcare provider. Off-Label Use Compounding Required