Low-dose naltrexone (LDN)

What is low-dose naltrexone (LDN)?

Low-dose naltrexone refers to naltrexone prescribed at doses typically between 0.5 mg and 6.0 mg per day — far below the standard 50 mg dose used for addiction treatment. The most commonly reported dose is 4.5 mg per day, usually taken at bedtime.

The theoretical basis for LDN is different from addiction treatment. At low doses, naltrexone is thought to:

• Briefly block opioid receptors, triggering a rebound increase in endogenous opioid production (endorphins and enkephalins)
• Modulate immune function through antagonism at Toll-like receptor 4 (TLR4) on microglial cells — a proposed anti-inflammatory mechanism

These are hypotheses. Human studies have not established one LDN mechanism that explains benefit across all of these conditions.

Low doses may require a pharmacy-prepared formulation where no suitable authorised strength is available. Do not improvise a liquid or divide a product unless a prescriber and pharmacist have confirmed the exact preparation and measurement.

The evidence by condition

A summary of clinical evidence for LDN across the most studied conditions. It is based on a 2026 narrative review of 105 studies (Advances in Therapy), with fibromyalgia trials published since then added.

1. Fibromyalgia. Early small crossover trials reported meaningful improvements in pain and mood, and case reports describe pain or fatigue falling by roughly 30–60%. Larger, more recent randomised trials have not confirmed this. The FINAL trial (99 women, 12 weeks) found no significant group-level difference in pain, and the INNOVA trial (98 women, 4.5 mg/day, published 2026) found no clinically meaningful benefit over placebo at 3 or 12 months. A 2024 meta-analysis of four earlier trials (222 patients) reported a small average pain reduction of 0.86 points on a 0–10 scale; it was completed before INNOVA was published, and whether that difference matters to patients is uncertain.
2. Chronic pain (other types). The 2026 review counts nine comparator trials across chronic pain conditions, fibromyalgia included: eight randomised trials and one non-randomised crossover study, with 430 participants in total. LDN has been studied in painful diabetic neuropathy (comparable to amitriptyline but better tolerated), osteoarthritis and inflammatory arthritis (no significant benefit over placebo in controlled trials), HIV-associated pain (no superiority over gabapentin or placebo), and complex regional pain syndrome. Retrospective studies report improvements but lack control groups. A consistent pattern: open-label studies report benefit, placebo-controlled trials show modest or no effect.
3. Multiple sclerosis. Two placebo-controlled crossover RCTs (n=60 and n=96) at 4.5 mg/day. The smaller trial found improvements in mental health quality of life and pain but not fatigue or physical function. The larger trial found no consistent benefits across quality of life domains (MSQoL-54). Evidence is inconclusive and inconsistent.
4. Autoimmune and gastrointestinal. Small studies in inflammatory bowel disease (Crohn’s, ulcerative colitis) show possible benefit but findings are inconsistent. Evidence for autoimmune conditions (lupus, rheumatoid arthritis) is predominantly from case reports and small uncontrolled series. No large-scale RCTs support routine use. Dermatological applications (psoriasis, eczema) are supported only by case reports.
5. Mental health and other. Studies in depression, PTSD, and post-infectious syndromes (including long COVID) are almost exclusively case reports and small uncontrolled series. The few placebo-controlled trials have not demonstrated clear clinical benefit. Oncological applications (cancer-related fatigue, tumour progression) are experimental with no controlled human evidence for efficacy.

What the data shows

Key figures from the 2026 narrative review (Advances in Therapy).

• Total studies reviewed: 105. 15 RCTs, the rest case reports, case series, and observational studies.
• Most common dose: 4.5 mg. Once daily, typically at bedtime. 0.5–6.0 mg range used across studies.
• Randomised controlled trials: 15. Across seven therapeutic areas, with 10 to 99 participants each. Most positive findings come from smaller or earlier studies.
• Evidence conclusion: Not routine. Review states current evidence ‘does not support routine clinical use’.

Questions worth settling before an LDN trial

Does the evidence fit my exact condition?

Evidence quality differs sharply by condition. Ask about the best controlled trials for your diagnosis, not a combined success claim across unrelated illnesses.

Does ‘low dose’ mean low risk?

Not automatically. Short studies often report tolerability, but long-term evidence is thinner. Opioid interactions, other medicines, pregnancy, liver health, formulation quality, and the risk of delaying proven care still matter.

How would I obtain the exact dose?

Availability depends on local authorised products and pharmacy-compounding rules. Use a prescriber and licensed pharmacist; do not improvise a dilution or measurement from an online recipe.

Is the mechanism proven?

The proposed transient receptor blockade and immune effects are hypotheses. They have not been shown to explain benefit across all conditions grouped under the LDN label.

What if I use opioid pain medicine?

Tell the prescriber before considering LDN. Even a lower naltrexone dose can affect opioid response or create withdrawal risk. In an emergency, tell the treating team that you take naltrexone and let them manage pain using the current clinical protocol.

How will we know whether it worked?

Agree on one or two measurable symptoms, a review date, a meaningful-change threshold, and a stopping rule. Also decide what evidence-based care continues during the trial.

Make an LDN trial answerable

If a clinician suggests LDN, agree on the symptom being measured, the review date, what counts as meaningful improvement, and when to stop. That turns an open-ended experiment into a decision.

Compare with approved naltrexone usesReview naltrexone safety

Sources

Checked October 22, 2026.

1. Low-Dose Naltrexone: What is the Evidence? A Narrative Review. Reviews 105 studies, including 15 randomised controlled trials, and emphasises the limits of routine clinical use.
2. Efficacy and safety of low-dose naltrexone for fibromyalgia, a systematic review and meta-analysis of randomised trials (2024) — Korean Journal of Pain; corrigendum 2026. Four RCTs, 222 patients, searched to May 2024, before INNOVA was published. The 2026 corrigendum changed the 30% responder odds ratio, not the pain-score result.
3. Efficacy of low-dose naltrexone in women with fibromyalgia, a 12-month randomised placebo-controlled trial (INNOVA) — European Journal of Pain, 2026. 98 women, LDN 4.5 mg/day; no clinically meaningful benefit over placebo at 3 or 12 months.
4. Symptom response to low-dose naltrexone in fibromyalgia, exploratory analysis of the FINAL trial — Pain Management Nursing, 2026. Summarises FINAL (99 women, 12 weeks; no significant group-level difference in pain).