What LDN Is

Naltrexone is a long-acting opioid receptor antagonist. At its standard 50 mg dose (sold under brand names like ReVia in some markets), it blocks opioid receptors and is used to treat opioid use disorder and alcohol use disorder.

“Low-dose naltrexone” or LDN refers to the off-label use of naltrexone at doses substantially below 50 mg—typically 1.5 mg, 3 mg, or 4.5 mg, sometimes up to 6 mg. At these much lower doses, naltrexone is proposed to have different effects than at the higher dose, working through several mechanisms that are not yet fully characterized.

Because LDN at these low doses isn’t a commercial product in Canada, patients receiving LDN obtain it through compounding pharmacies that prepare lower-strength capsules from raw naltrexone hydrochloride.

How LDN Is Proposed to Work

The mechanisms underlying LDN’s reported effects are not fully established, and ongoing research continues to investigate them. Two main mechanisms are most discussed in the literature:

1. Brief, Partial Opioid Receptor Blockade with Endorphin Upregulation

The hypothesis suggests that brief, partial blockade of opioid receptors at low doses—lasting only a few hours—triggers compensatory upregulation of endogenous opioids (endorphins, met-enkephalin). After the LDN clears the system, the upregulated endogenous opioid signaling provides modulation of pain and inflammatory pathways.

2. Toll-Like Receptor 4 (TLR4) Antagonism on Microglia

LDN has been shown to antagonize TLR4 on microglial cells. Microglial activation contributes to neuroinflammation and central sensitization in chronic pain states. By reducing TLR4-mediated microglial activation, LDN may attenuate neuroinflammatory signaling.

Either of these mechanisms (or both, or others not yet identified) may underlie the clinical effects some patients experience. The mechanism question matters because it affects what conditions LDN might help with—and where it’s unlikely to help.

What the Evidence Says

LDN has been studied for several conditions, with varying levels of evidence quality.

Fibromyalgia

The most-studied indication for LDN. Multiple small randomized controlled trials and observational studies suggest LDN may produce modest improvements in pain, sleep, and quality of life in fibromyalgia patients. Effect sizes are modest, and not all patients respond, but the evidence base is the strongest for this indication. Major reviews acknowledge LDN as a reasonable option to consider in fibromyalgia, though not a guaranteed solution.

Crohn’s Disease and Inflammatory Bowel Disease

Small RCTs and observational studies have suggested LDN may produce mucosal healing in some patients with active Crohn’s disease. The evidence is intriguing but not yet sufficient to make LDN a standard treatment. Some gastroenterologists use it as an adjunct option in selected cases.

Multiple Sclerosis Symptom Management

Studies have explored LDN for MS-related symptoms (spasticity, fatigue, quality of life). Results are mixed; some studies show benefit, others don’t. LDN doesn’t appear to modify the underlying disease course of MS—it’s used for symptom management when it’s used.

Chronic Pain (General)

Outside of fibromyalgia, evidence for LDN in chronic pain is largely observational and based on case series. Some patients with various chronic pain conditions report meaningful benefit; others don’t. The lack of robust controlled trial evidence in many specific pain conditions means LDN use in these settings is largely based on clinical experience rather than strong evidence.

Autoimmune Conditions

LDN has been used adjunctively in conditions like Hashimoto’s thyroiditis, lupus, and rheumatoid arthritis based on observational data and theoretical mechanism. RCT evidence in these conditions is limited.

Long COVID

An emerging area where LDN is being investigated. Case series have suggested possible benefit for some patients with post-acute COVID symptoms, but evidence is preliminary.

Complex Regional Pain Syndrome (CRPS)

Case reports and small case series. Evidence is limited.

Common Dosing Approaches

There is no single standardized LDN dosing protocol. Common approaches in clinical practice:

Standard Titration

• Weeks 1–2: 1.5 mg at bedtime
• Weeks 3–4: 3 mg at bedtime if 1.5 mg tolerated
• Week 5+: 4.5 mg at bedtime if 3 mg tolerated
• Reassess at 8–12 weeks for clinical response

Slower Titration for Sensitive Patients

Patients with histories of medication sensitivity or anxiety about side effects may benefit from a slower approach—starting at 0.5 mg or 1 mg and increasing more gradually. Custom-strength capsules or liquid suspension can support this.

Bedtime vs. Morning Dosing

Bedtime dosing is more common in the literature. Some patients experience LDN-related vivid dreams or sleep disruption at bedtime; in these cases, evening or morning dosing is sometimes used. Your prescriber decides timing based on your situation.

Common Side Effects

LDN is generally well-tolerated. Reported side effects (typically transient, often resolving with continued use or dose adjustment):

• Vivid dreams (most common with bedtime dosing; usually resolves in 1–2 weeks)
• Insomnia or sleep disruption
• Headache
• Nausea or GI upset
• Fatigue (typically transient)
• Anxiety (less common)

Side effects are often dose-dependent. Slowing titration or temporarily reducing the dose typically resolves them.

Important Cautions and Contraindications

Absolute Contraindication: Concurrent Opioid Use

This is the most important safety point. LDN—even at low doses—can:

• Precipitate withdrawal in opioid-dependent patients
• Block the analgesic effect of opioids if needed for acute pain

Patients on opioids cannot safely use LDN. Patients on LDN cannot use opioid medications during the period LDN is active. This includes:

• Prescription opioids (codeine, tramadol, oxycodone, hydromorphone, morphine, fentanyl, etc.)
• Some over-the-counter products containing opioids (codeine-containing cough preparations in some jurisdictions)
• Surgical or post-surgical opioid analgesia—LDN should typically be discontinued 24–72 hours before procedures requiring opioids

Patients on LDN must inform dental, surgical, and emergency providers about LDN use because it affects acute pain management options.

Other Cautions

• Hepatic impairment: Naltrexone is hepatically metabolized. Patients with significant liver disease may need monitoring or dose adjustment.
• Pregnancy and lactation: Limited safety data. Generally avoided unless clinical benefit clearly outweighs theoretical risk.
• Active substance use disorder: LDN is not a substitute for standard naltrexone treatment of opioid or alcohol use disorder.

What Patients Often Ask

“Will LDN help me?”

Honestly, no one can predict in advance who will respond to LDN. Some patients have meaningful improvement; others don’t. The decision to try LDN is a calculated decision based on your specific condition, what else you’ve tried, your prescriber’s clinical assessment, and a willingness to trial it for 8–12 weeks before judging response.

“How quickly will I feel different?”

LDN effects are typically gradual. Many patients don’t notice meaningful change in the first 2–4 weeks. By 8–12 weeks, you should have a sense of whether it’s helping. Patients expecting quick relief often discontinue before the medication has had time to work.

“How long will I need to take it?”

If LDN is helping, many patients continue indefinitely. Some try discontinuing periodically to see if symptoms recur. If LDN isn’t helping after a sufficient trial, discontinuation is reasonable.

“Can I take LDN with other medications?”

Most non-opioid medications are compatible with LDN. The major exception is opioids (covered above). For other interactions, your pharmacist and prescriber can review your specific medications.

“What if I need pain medication for a sudden injury or surgery?”

If you’re on LDN and need acute pain management, the LDN typically needs to be discontinued before opioid analgesia. Plan with your prescriber and surgical or dental team in advance when possible. For unexpected emergencies, inform the treating physician about your LDN use.

Compounded LDN: What We Prepare

Standard Strengths

• 1.5 mg capsules (typical starting dose)
• 3 mg capsules (typical intermediate dose)
• 4.5 mg capsules (typical target dose)

Custom Strengths Available

• 0.5 mg, 1 mg, 2 mg, 3.5 mg, 5 mg, 6 mg
• Liquid suspensions for fine titration

Quality and Safety

We use pharmaceutical-grade naltrexone hydrochloride from verified suppliers, with documented batch records, ingredient lot tracking, and pharmacist verification. Compounded LDN preparations are stable for typical refill cycles when stored as directed.

If Your Prescriber Is Considering LDN

Useful questions to discuss with your prescriber:

• What’s the rationale for considering LDN for my specific condition?
• What’s the realistic expected benefit—what would success look like?
• What’s the timeline before we’d judge whether it’s working?
• What’s the titration plan, and what should I do if I have side effects?
• What are the alternatives we’ve tried or are considering?
• What other components should be part of my treatment plan?

If your prescriber is unfamiliar with LDN but open to learning more, our pharmacist can speak with them about formulation considerations, common dosing approaches, and ingredient information. Clinical decisions about whether to prescribe remain with your prescriber.