Naltrexone, along with naloxone are narcotic (opioid) antidotes, that is they counteract the effect of narcotics and are used to treat overdoses with heroin, fentanyl, Percocet, Vicodin, and other opioid drugs. Surprisingly, low doses of naltrexone (LDN) seem to be effective in treating pain. LDN has been also used to treat symptom in conditions such as depression, fibromyalgia, Crohn’s disease, multiple sclerosis, complex regional pain syndrome (which used to be called reflex sympathetic dystrophy), and autoimmune disorders.
Low dose naltrexone is not a typical pain killer, but may be helping pain by reducing inflammation. Instead of opioid receptors, it works on Toll-like receptor 4 (TLR4) receptors on glial cells. Glial cells surround the nerve cells and play important functions in the brain, beyond just a supporting role that had been assigned to them for many years. Opioid drugs are known to promote inflammation through the brain immune system leading to worsening of pain over time. Recent discoveries have shown that the Toll-like receptors are involved in triggering these inflammatory immune events. These discoveries have led many researchers to look at ways to block TLR4, but so far no such drug has been developed. We do have several existing medications that seem to block TLR4. Besides LDN, amitriptyline (Elavil) and cyclobenzaprine (Flexeril) are two other drugs that block TLR4 and that have been used for years to treat pain.
No large controlled studies of LDN for migraines, pain or any other condition have been conducted to date. Despite the fact that the evidence is only anecdotal and that LDN my work purely through the placebo effect, advantages of LDN are that it is inexpensive and safe. Naltrexone is available in 25 and 50 mg tablets, while the amount used for LDN is between 1.5 to 4.5 mg. This means that it can be obtained only from a compounding pharmacy. Naltrexone is not a controlled substance, but it does require a prescription from the doctor.
