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Compounded · Not FDA-approved

Low-dose naltrexone (LDN): uses, dosing, side effects and where to get it

An opioid blocker approved at 50 mg for alcohol and opioid dependence. At about a tenth of that dose it is compounded and prescribed off-label for pain and inflammation; recent trials found no benefit over placebo for fibromyalgia, and none has tested it for aging.

White tablets in a small ceramic dish on warm limestone

By the RxLineup editorial team · Fact-checked against provider sites and FDA labels · Updated

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Active ingredient
Naltrexone hydrochloride
Made by
Compounding pharmacies, from the approved drug naltrexone
Form
Capsule, tablet or troche
Price online
Prices vary by clinic.

Safety

Naltrexone blocks opioids: taking it while using opioids can bring on sudden withdrawal, and it stops opioid pain medicine from working. Naltrexone labels also warn about liver injury and a higher risk of overdose if opioids are used after stopping it. In the 12-month trial, side effects were mostly mild and short-lived, and about as common as on placebo.

Talk to a licensed clinician about your health history and every medication you take before you start.

Prescription only; the ingredient has an FDA-approved form, but compounded versions are not FDA-approved, and this use is off-label. Low-dose naltrexone (LDN) is prepared by a compounding pharmacy for an individual prescription. Compounded products are not FDA-approved, and the FDA does not review them for safety, effectiveness or quality. Its use for longevity is off-label: a use the FDA label does not cover, which a clinician may still choose. Naltrexone is FDA-approved at 50 mg; low-dose versions are compounded from it for individual prescriptions under section 503A. The low-dose uses have not been reviewed by the FDA. Naltrexone is not a controlled substance.

What low-dose naltrexone (LDN) is

Low-dose naltrexone (LDN) contains naltrexone hydrochloride. Low doses (about 0.5 mg to 4.5 mg) are compounded from approved naltrexone and prescribed off-label.

What the FDA has approved

  • Naltrexone 50 mg tablets and Vivitrol injection are approved for alcohol dependence and for blocking the effects of opioids
  • No low-dose product is approved

Dosing

Capsule, tablet or troche, once a day in the trials below; your prescriber sets the schedule. Usually 0.5 mg to 4.5 mg a day. Clinics we checked sell 1 mg to 4.5 mg capsules; the trials below used 4.5 mg.

How well it works

Evidence is mostly about pain, not aging, and recent trials are negative. In a crossover trial of 58 people with fibromyalgia, 4.5 mg a day did not reduce pain or symptom scores more than placebo (Bested 2023). A 12-month trial in 98 women with fibromyalgia found no clinically meaningful benefit (INNOVA, 2026). No trial has tested LDN for aging or lifespan. Individual results vary.

Low-dose naltrexone (LDN) cost

Prices vary by clinic.

Questions, answered

How much does low-dose naltrexone (LDN) cost online?
Prices vary by clinic.

Is low-dose naltrexone (LDN) FDA-approved?
No. Low-dose naltrexone (LDN) is compounded: a compounding pharmacy prepares it for an individual prescription, and it isn’t FDA-approved. Naltrexone is FDA-approved at 50 mg; low-dose versions are compounded from it for individual prescriptions under section 503A. The low-dose uses have not been reviewed by the FDA. Naltrexone is not a controlled substance.

How do you take low-dose naltrexone (LDN)?
Capsule, tablet or troche, once a day in the trials below; your prescriber sets the schedule. Usually 0.5 mg to 4.5 mg a day. Clinics we checked sell 1 mg to 4.5 mg capsules; the trials below used 4.5 mg.

What are the risks of low-dose naltrexone (LDN)?
Naltrexone blocks opioids: taking it while using opioids can bring on sudden withdrawal, and it stops opioid pain medicine from working. Naltrexone labels also warn about liver injury and a higher risk of overdose if opioids are used after stopping it. In the 12-month trial, side effects were mostly mild and short-lived, and about as common as on placebo.

Can I get low-dose naltrexone (LDN) online?
A licensed clinician can prescribe low-dose naltrexone (LDN) after an online or in-person visit.

Sources

  1. Vivitrol (naltrexone) prescribing information (DailyMed)
  2. Drugs@FDA: naltrexone hydrochloride tablets, NDA 018932
  3. Bested et al. 2023: low-dose naltrexone for fibromyalgia pain (Pain Reports)
  4. Rodríguez-Freire et al. 2026: the 12-month INNOVA trial (European Journal of Pain)
  5. FDA: bulk drug substances used in compounding under section 503A (Category 1 list updated May 14, 2026)
  6. DEA: controlled substances, alphabetical order (Aug 27, 2026)