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Prescription medication — not a dietary supplement
Low-Dose Naltrexone (LDN)is a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Most Low-Dose Naltrexone (LDN) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality meta-analyses and randomised trials published 2007–2025 with a typical study size of 31 participants.
Based on 7 studies · 1 meta-analysis · 3 RCTs · 234 total participants
Confidence
ModerateBy outcome
Low-Dose Naltrexone (LDN) has an evidence score of 3.8/10 — emerging evidence based on 7 indexed studies, including 2 meta-analyses. An opioid-antagonist drug (naltrexone) taken off-label at very low doses (~1.5–4.5 mg) for chronic pain, fibromyalgia, and autoimmune/inflammatory conditions. The leading idea is that a brief nightly opioid-receptor blockade triggers a rebound rise in endorphins and dampens glial/TLR4 inflammation. Human trials are mostly small pilots with mixed results — a real but preliminary signal in fibromyalgia, weaker elsewhere. A prescription drug used off-label, not a supplement, and not a proven longevity drug. Representative study: PMID 40540205.
The commonly studied dose of Low-Dose Naltrexone (LDN) is Off-label, prescription-only. Typical LDN dosing is ~1.5–4.5 mg once daily, usually at night, often started low (~1.5 mg) and titrated to 4.5 mg. Requires a compounding pharmacy (commercial tablets are 50 mg). Not an approved or standardized regimen.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Last reviewed June 2026 · evidence from 7 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Low-dose naltrexone (LDN) — off-label opioid antagonist
An opioid-antagonist drug (naltrexone) taken off-label at very low doses (~1.5–4.5 mg) for chronic pain, fibromyalgia, and autoimmune/inflammatory conditions. The leading idea is that a brief nightly opioid-receptor blockade triggers a rebound rise in endorphins and dampens glial/TLR4 inflammation. Human trials are mostly small pilots with mixed results — a real but preliminary signal in fibromyalgia, weaker elsewhere. A prescription drug used off-label, not a supplement, and not a proven longevity drug.
LDN has a mechanistically plausible anti-inflammatory rationale (transient opioid-receptor blockade with endorphin rebound plus TLR4/glial suppression) and a genuine human pain signal in fibromyalgia — small Stanford RCTs showed ~30% pain reductions and a 2025 meta-analysis confirmed a modest fibromyalgia benefit. But every trial is small, short, and mostly crossover; pooled and parallel-group results are mixed-to-null (a 2025 systematic review found no superiority over placebo, and an MS quality-of-life RCT was negative); the mechanism is partly hypothesized; and there are no human longevity outcomes — so it stays emerging.
Naltrexone is an FDA-approved opioid antagonist used at 50 mg/day for alcohol and opioid use disorder. 'Low-dose naltrexone' (LDN) is the same molecule taken at roughly 1.5–4.5 mg, almost always at night, for an entirely different set of off-label indications — fibromyalgia and chronic pain, and autoimmune/inflammatory conditions such as Crohn's disease and multiple sclerosis.
The proposed mechanism is genuinely interesting but still partly hypothesized: a low dose produces only a brief, transient blockade of opioid receptors, which is thought to trigger a compensatory rebound increase in endogenous opioids (endorphins and enkephalins) and upregulation of opioid receptors.
Separately — and probably more relevant to the anti-inflammatory claims — naltrexone (and its stereoisomer) antagonises Toll-like receptor 4 (TLR4) on microglia and other glial cells, which can suppress glial activation and the release of pro-inflammatory cytokines that drive central sensitisation in chronic-pain states.
The honest picture of the evidence: the strongest human data are in fibromyalgia, where Stanford pilot and small crossover RCTs (Younger and colleagues) found ~30% pain reductions versus placebo, and a 2025 chronic-pain meta-analysis confirmed a modest but significant benefit specifically in fibromyalgia.
But the trials are uniformly small (tens of participants), short, and crossover in design; a 2025 systematic review of fibromyalgia found that while LDN improved pain versus baseline, it was not statistically superior to placebo when pooled, and a parallel-group MS quality-of-life RCT found no meaningful QoL benefit.
So the evidence base is preliminary and mixed, not settled. The Crohn's data are limited to small open-label and pilot work.
LDN is generally well tolerated — the most common effects are sleep disturbance and vivid dreams — but it must not be combined with opioid pain medication (it blocks them and can precipitate withdrawal), and it requires a prescription and compounding (commercial tablets are 50 mg).
Some in the longevity community frame LDN as an 'inflammaging' / immune-modulation tool, but there are no human longevity or lifespan outcomes — that framing is speculative.
The score reflects a real, mechanistically plausible, and reasonably well-tolerated off-label option with a genuine fibromyalgia pain signal, set against small-sample preliminary trials, mixed/negative pooled and parallel-group results, and no longevity evidence.
A very low nightly dose briefly antagonises opioid receptors. The short blockade is thought to trigger a compensatory rebound rise in endogenous opioids (endorphins/enkephalins) and receptor upregulation.
Naltrexone antagonises Toll-like receptor 4 on microglia and other glia, dampening glial activation and pro-inflammatory cytokine release that drive central sensitisation in chronic pain.
The proposed rise in endogenous opioids and enkephalins is invoked to explain mood, pain, and immune-modulatory effects in autoimmune conditions — though this part of the mechanism remains partly hypothesized.
How Low-Dose Naltrexone (LDN) works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
Off-label, prescription-only. Typical LDN dosing is ~1.5–4.5 mg once daily, usually at night, often started low (~1.5 mg) and titrated to 4.5 mg. Requires a compounding pharmacy (commercial tablets are 50 mg). Not an approved or standardized regimen.
Can be taken without food
| Form | Type |
|---|---|
| 💊Compounded low-dose (1.5–4.5 mg) capsule or liquid | Recommended |
Requires a prescription and a compounding pharmacy; standard commercial naltrexone is 50 mg, far above the LDN range.
Minimum: 8 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Usually dosed at night. Allow several weeks for a pain effect. Never combine with opioid analgesics.
Dose-response data unavailable. The current published research for Low-Dose Naltrexone (LDN) does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Small randomized trials showed ~30% reductions in fibromyalgia pain versus placebo; the strongest LDN signal.
Proposed glial/TLR4 suppression underlies use in Crohn's disease and other inflammatory conditions — evidence here is small and preliminary.
Pooled and parallel-group analyses are mixed-to-null — a fibromyalgia systematic review found no superiority over placebo, and an MS quality-of-life RCT was negative.
The most common side effect; usually mild and transient. Generally very well tolerated otherwise.
Avoid — LDN blocks opioids and can precipitate withdrawal.
Use with caution under clinician supervision.
Not established as safe at low dose; discuss with a clinician.
Naltrexone blocks opioid receptors — it negates opioid pain relief and can precipitate acute withdrawal in opioid-dependent people. The defining LDN interaction.
Naltrexone is metabolised by the liver; caution with other hepatically-stressing agents, though LDN doses are far below the levels associated with liver effects.
Tip: Most common LDN effect; often transient. Some clinicians switch to morning dosing if it persists.
Tip: Usually mild; starting low (~1.5 mg) and titrating helps.
Tip: Do not use with opioid pain medication; ensure an opioid-free interval before starting.
The best time to take Low-Dose Naltrexone (LDN) is in the evening. It can be taken on an empty stomach. Most trials dosed 4.5 mg at night; a transient overnight blockade is the intended pharmacology.
Low-Dose Naltrexone (LDN) should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are sleep disturbance / vivid dreams, headache / nausea, loss of opioid analgesia / withdrawal. Use caution if any of these apply to you: Current opioid use or opioid pain medication (precipitates withdrawal / blocks analgesia); Acute opioid withdrawal; Significant hepatic impairment (naltrexone is hepatically metabolised).
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