Low-dose naltrexone (LDN) is the term review abstracts use for naltrexone taken at doses lower than the 50 mg tablet. One 2026 review abstract describes it as commonly 1-6 mg/day and as used off-label. The ways it might work are proposed ideas, and this guide keeps LDN separate from the FDA-approved 50 mg tablet.
What the term means
The sources do not give one fixed dose. The same 2026 review abstract says LDN is increasingly used off-label for chronic pain, although evidence specific to neuropathic pain remains uncertain. A 2026 narrative review abstract says naltrexone is prescribed off-label at low doses, typically 0.5-6.0 mg, for a variety of therapeutic indications. A 2018 review abstract considers LDN in a daily dose of 1 to 5 mg.
The 50 mg tablet is a separate product
The prescribing information for naltrexone hydrochloride tablets, USP 50 mg (revised 05/2026) describes naltrexone as an opioid antagonist that is a synthetic congener of oxymorphone with no opioid agonist properties. The same label says the tablets are indicated in the treatment of alcohol dependence and for the blockade of the effects of exogenously administered opioids, and that they are film-coated tablets containing 50 mg. It also says naltrexone hydrochloride blocks the effects of opioids by competitive binding at opioid receptors. Those statements are about the 50 mg tablet. They are not statements about LDN.
Proposed ways it might work
The sources below are reviews, not trials, and they word these ideas differently.
| Idea | What the source says |
|---|---|
| T cells, B cells and Toll-like receptor 4 (TLR4) | A 2018 Pharmacotherapy review abstract says it is hypothesized that lower than standard doses of naltrexone inhibit cellular proliferation of T and B cells and block Toll-like receptor 4, resulting in an analgesic and antiinflammatory effect. |
| Microglial cells | A 2014 review abstract reviews the evidence that LDN may operate as a novel anti-inflammatory agent in the central nervous system, via action on microglial cells. |
| Glial response | A 2018 Medical Sciences review abstract states that LDN, considered in a daily dose of 1 to 5 mg, has been shown to reduce glial inflammatory response by modulating TLR4 signaling and by transient opioid-receptor blockade. |
| Opioid growth factor receptor (OGFr) | A 2015 review abstract says an intermittent OGFr blockade by low dosages of naltrexone resulted in depressed cell replication, whereas high or sustained dosages that conferred a continuous OGFr blockade resulted in enhanced growth. |
| A caution | A 2026 review abstract on neuropathic pain says the TLR4-microglial rationale is plausible, but measured plasma concentrations at 4.5 mg/day fall several orders of magnitude below those associated with TLR4 inhibition in vitro. |
LDN is an off-label use
A 2018 review abstract says LDN has been used off-label for pain and inflammation in multiple sclerosis, Crohn's disease, fibromyalgia, and other diseases. That describes use. It does not show benefit in any one condition.
An FDA patient page on off-label use says that, from the FDA perspective, healthcare providers generally may prescribe an approved drug for an unapproved use when they judge that it is medically appropriate for their patient. The same page says FDA has not determined that the drug is safe and effective for the unapproved use.
Where LDN is supplied as a compounded drug, an FDA questions-and-answers page states that compounded drugs are not FDA-approved. It says this means FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed.
What this does not tell you
These are proposed explanations from review abstracts. This guide does not show that any of them happens in people at these doses, or that any of them leads to a benefit. The abstracts differ in wording, from "hypothesized" to "has been shown", and one adds a caution about plasma concentrations.
Statements in the 50 mg tablet label, including its warnings and adverse reaction rates, are about that tablet and do not carry over to LDN. A use described for one condition does not apply to another. Whether LDN suits a particular person is for a licensed provider to decide.