Naltrexone is a member of a class of drugs known as an opiate antagonists. It blocks the effects of opiate drugs such as as heroin and morphine and as such is often used as part of treatment programs for addiction to these drugs. For this purpose the dose is usually between 50 and 150mg daily.
When used in low doses (1.5 to 4.5mg daily) however it has entirely different effects and is being used "off-label" to treat people with autoimmune diseases including multiple sclerosis (MS) and Crohn's disease, as well as environmental illnesses including chronic fatigue syndrome (ME/CFS), fibromyalgia, irritable bowel syndrome (IBS) and autism. It may also be effective in mood disorders such as depression and bipolar disorder for reasons that will become apparent.
Low-dose Naltrexone (LDN) therapy was developed by Dr. Bernard Bihari, a neurophysician in New York, USA. Dr. Bihari is qualified in Internal Medicine, Psychiatry and Neurology. LDN has been used in the USA since 1985 but has only recently started to be used by doctors in the UK and mainland Europe.
LDN is thought to work by temporarily inhibiting the action of endorphins (the body's own opioids) which has the rebound effect of stimulating the body to produce larger amounts of endorphins. The diseases treated with LDN typically involve abnormally low levels of endorphins. Restoration of normal levels of endorphins by LDN should have the effect of reducing pain and increasing mood, energy and an individual's general sense of well-being.
However, these are not the only effects of LDN - perhaps more important are the effects increased endorphin levels have on the immune system. Increased endorphins have been shown by Dr. Bihari and others to stimulate the immune system, specifically producing an increase in the number of T lymphocytes. In particular, LDN appears to restore normal levels of T suppressor cells - these cells normally prevent the runaway immune reactions that lead to autoimmune and allergic diseases. Additionally, LDN is thought to restore a normal balance between the Th1 and Th2 branches of the immune system which would be expected to reduce the production of antibodies against the body's own tissues (autoimmune disease) and environmental antigens such as pollen and mold (allergies). An abnormal dominance of Th2 immune activity has frequently been noted in environmental illnesses and LDN would therefore be expected to be beneficial. Also of importance is evidence that LDN restores numbers of Natural Killer (NK) cells - an important part of Th1 immunity - which have consistently been shown to be low in chronic fatigue syndrome and other environmental illnesses.
In summary, the effects of LDN on the immune system in theory reduce abnormal reactions to the body's own tissues and allergens and increase the ability of the body to fight infectious agents including viruses, bacteria and yeasts/fungi (e.g. Candida).
The introductory dose of 1.5mg LDN is usually taken for the first 2 weeks of treatment, then increased by 0.5mg every 2 weeks until the individual finds the dose that suits them best (up to the maximum of 4.5mg). If there is an increase in symptoms when taking a higher dose it might indicate that this dose is too high. Lowering the dose should result in improvements becoming apparent.
LDN only stays in the system for 4 hours and most people take it before bed as the temporary blocking of the effects of endorphins can be uncomfortable whilst awake (e.g. increased pain, lowered mood). However, some people find taking LDN at night causes disturbed sleep so taking the dose in the morning is preferable for them.
Groups promoting LDN, whilst noting a patient's symptoms more initially become more severe and sleep disturbances and constipation may occur, suggest these effects or usually last only a couple of weeks and then improvements will be seen in most cases. They do caution that clinical trials have not been performed on LDN however so the possibility of long-term side-effects cannot be ruled out.