Low Dose Naltrexone

Low Dose Naltrexone

Low Dose Naltrexone (LDN) holds the potential to help millions of people suffering from various autoimmune diseases and cancers, and even autism, chronic fatigue, and depression find relief. Administered off-label in small daily doses (0.5 to 4.5 mg), this generic drug is extremely affordable and presents few known side effects. So why has it languished in relative medical obscurity?


The LDN Book explains the drug’s origins, its primary mechanism, and the latest research from practicing physicians and pharmacists as compiled by Linda Elsegood of The LDN Research Trust, the world’s largest LDN charity organization with over 19,000 members worldwide. Featuring ten chapters contributed by medical professionals on LDN’s efficacy and two patient-friendly appendices, The LDN Book is a comprehensive resource for doctors, pharmacists, and patients who want to learn more about how LDN is helping people now, and a clarion call for further research that could help millions more.

How Low Dose Naltrexone Works

LDN is most commonly being used for Chronic Fatigue, Multiple Sclerosis, Myalgia Encephalopathy, autoimmune thyroid diseases and various cancers. Many autoimmune diseases seem to respond to LDN.

This is a wide range of diseases and many clinicians will find it difficult to understand how one drug can have a positive effect on all these pathologies.


The first thing to understand is that Naltrexone – the drug in LDN – comes in a 50:50 mixture of 2 different shapes (called isomers). It has been recently discovered that one particular shape binds to immune cells, whilst the other shape binds to opioid receptors.

Although consisting of exactly the same components, the two isomers appear to have different biological activity.

Summary of Mechanism of Action

The summary of 10 years of research is that LDN works because:

Levo-Naltrexone is an antagonist for the opiate/endorphin receptors

  • This causes increased endorphin release
  • Increased endorphins modulate the immune response
  • This reduces the speed of unwanted cells growing Dextro-Naltrexone is an antagonist for at least one, if not more immune cells
  • Antagonizes “TLR,” suppressing cytokine modulated immune system
  •  Antagonizes TLR-mediated production of NF-kB – reducing inflammation, potentially downregulating oncogenes

Taking Naltrexone in larger doses of 50-300mg seems to negate the immunomodulatory effect by overwhelming the receptors, so for the effect to work, the dose must be in the range of 0.5-10mg, usually maxing at 4.5mg in clinical experience.

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