What is LDN (Low Dose Naltrexone)?


Naltrexone is in a class of drug known as an opiate antagonists. Its normal use is in treating addiction to opiate drugs such as heroin or morphine. The dose used for this purpose is usually between 50 and 300mg daily. 

Low-dose Naltrexone (LDN) has been used in the treatment of autoimmune diseases in the USA since 1985, but is relatively new in the United Kingdom and Europe. Despite the fact that the drug is used at a very low dose, the occurrence of significant introductory or long term side effects cannot be excluded. 

This method was devised and subsequently developed by the late Dr Bernard Bihari, M.D., a physician from New York, USA who passed away May 16, 2010. Dr Bihari was qualified in Internal Medicine, Psychiatry and Neurology, and we hope to honor him by continuing his pioneering work.

Suggested Method of Therapy

Your doctor will usually start treatment at an ultra-low dose and increase this gradually over a period of weeks – until you are stable and side effect free.

The starting dose can vary from 0.5mg to 1.5mg – and is usually increased over 4 - 8 weeks to 4.5mg or higher until the optimal dose is reached. Some doctors increase this to twice daily, for certain medical conditions.

For Autoimmune Diseases, patients typically start at 1mg and increase to 4.5mg daily over a period of 4 weeks.

However, for Hashimoto's Thyroiditis, Chronic Fatigue Syndrome or Fibromyalgia, the starting dose is usually 0.5mg and is increased by 0.5mg a week until a daily dose of 4.5mg is reached if tolerated.

For Cancer, LDN can be taken at similar doses, but must be avoided the week before and the week after cancer chemotherapy. This does not include a drug called tamoxifen or daily medications for prostate cancer.

Please Note: With LDN it isn't the higher the dose the better the benefit it is what dose suits you best, this might be as low as 2mg, not everyone gets to 4.5mg

How Naltrexone Works


As of 2016, LDN is most commonly being used for Chronic Fatigue, Multiple Sclerosis, Myelagic 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
  • Antagonises “TLR,” suppressing cytokine modulated immune system
  •  Antagonises 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.

The Use of Low-dose Naltrexone, and the Occurrence of Side Effects

Many patients who start LDN do not experience any severe side effects.

As mentioned earlier, your symptoms may become worse – in MS, this can be characterised by increased fatigue or increased spasticity. In CFS/ME, this can be the onset of apparent flu-like symptoms. LDN can cause sleep disturbances if taken at nighttime – this is most likely because of the increase in endorphin release. These disturbances can take the form of vivid dreams or insomnia.

In various studies (and anecdotal accounts), the number of T-Lymphocytes has been shown to dramatically increase when a patient starts on LDN. This may account for some of the benefits patients feel when they are being treated for an autoimmune disease or cancer. This has not been directly evidenced in multiple sclerosis.

Clinical experience shows that in less than ten percent of cases treated, increased introductory symptoms may be more severe or more prolonged than usual, lasting sometimes for several weeks. Rarely, symptoms may persist for two or three months before the appropriate beneficial response is achieved.

If side effects are troublesome, then reducing your dose by 50% for 7 days, before increasing it again, is a good idea.

Some patients, very rarely, experience gastrointestinal side effects, such as nausea and or constipation/diarrhea. The reason for this is currently unknown, but may be due to the presence of large numbers of delta-opiate receptors in the intestines.

Patients experiencing this side effect can request LDN Sublingual Drops, which transfer the LDN directly into the bloodstream – avoiding the GI tract.

Patients who do have these side effects should increase their dose by no more than 0.5mg per week and should consult with their GP or pharmacist for appropriate treatment for the stomach upset, if necessary. (Omeprazole, Ranitidine, Gaviscon, Fybogel, Mucogel and Pepto Bismol are ok – but not Kaolin & Morphine or Loperamide/Imodium.)

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