Low Dose Naltrexone (LDN) Provides Surprising Pain Relief

There are two powerful opioid antagonists: 1) naloxone (Narcan) given as an injection or nasal spray in the case of narcotic overdose and 2) naltrexone administered orally in the treatment of alcohol dependence and to block opioid activity in the brain. There is a growing interest in low dose naltrexone (LDN) for the treatment of pain. Doses range from 1 to 4.5 mg instead of the standard 50 to 100 mg dose.

A Very Old Drug!

The FDA approved naltrexone (Trexan) in 1984 to treat people with opioid use disorder. Most physicians have never heard of low dose naltrexone (LDN) because the FDA has never approved this drug for pain.

Q. I suffer from arthritis pain in my joints and muscle pain due to old injuries as an athlete. This limits my ability to exercise. I have hypothyroidism, so I have difficulty losing weight and managing my blood pressure as a result of the ongoing pain as well as the NSAIDs I take for it.

I have read about low dose naltrexone (LDN) and have discussed it with my primary care provider. He insists I should stick to aspirin and NSAIDs. Given the reported safety and effectiveness of LDN, why don’t doctors prescribe it? This is particularly irksome since there is so much concern about opiates.

A. At low doses (1 to 4.5 mg) naltrexone is prescribed to ease the pain and inflammation associated with conditions such as fibromyalgia, chronic pain syndrome, MS and Crohn’s disease (Current Pain and Headache Reports, Aug. 26, 2020).

There are reports that the drug can help treat a range of other health problems with minimal side effects (Clinical Rheumatology, online, Feb. 15, 2014). Keep in mind that a doctor who is prescribing LDN is doing so off label.

Because this is an old, inexpensive generic medication, pharmaceutical companies have no incentive to conduct research on it. Consequently, large, well-controlled clinical trials of low dose naltrexone (LDN) are scarce.

That may be why your doctor is reluctant to prescribe it. Researchers reviewing Norwegian prescription records concluded that when people start taking LDN, they seem to need less of other pain-relieving medicines such as NSAIDs (PLoS One, Feb. 14, 2019).

Most people tolerate LDN well, although some report nausea, nightmares or vivid dreams. Taking it in the morning may minimize sleep disturbances.

Here is another report from a reader.

Chronic Pain Relief:

Q. I have dealt with body pain for many years. Like the proverbial frog in boiling water, my pain increased gradually over the years and I just dealt with it. I wasn’t using meds because I seem to have so many side effects from them.

This summer my doctor put me on low dose naltrexone (LDN). It is not an opioid.

Medical oversight is essential for people switching from opioids to LDN. Not all doctors know about low dose naltrexone, so it is essential to find a doctor who is experienced in prescribing this medicine.

LDN has definitely helped me with my pain. I can even think and do activities. I have not noticed any side effects.

The studies of LDN are very interesting and there is potential that it might be used for more than just pain.

A. Far from being an opioid, naltrexone blocks opioid receptors. You may have heard of a similar drug, naloxone. When injected or administered as a nasal spray (Narcan) this opioid antagonist has life-saving ability. It rescues people who have overdosed on a narcotic and are on death’s doorstep.

New Uses for Low Dose Naltrexone (LDN)

Low dose naltrexone (LDN) is being investigated for its ability to relieve the pain of fibromyalgia (Current Rheumatology Reviews, March 21, 2017).  People are also considering it as a possible treatment for Crohn’s disease, multiple sclerosis, chronic fatigue syndrome and ALS aka Lou Gehrig’s disease (NIPH Systematic Reviews, April 2015).

While you are right that the studies are interesting, a lot more research is needed to determine which conditions might respond well to LDN. It appears that this treatment is nontoxic as well as affordable (Multiple Sclerosis Journal–Experimental, Translational and Clinical, Sep. 29, 2016).

How Does Low Dose Naltrexone (LDN) Work?

There are several proposed mechanisms of action for this drug. The leading hypothesis is that LDN blocks opioid receptors. The body then compensates by manufacturing its own natural (endogenous) opioids. LDN may also have anti-inflammatory activity. Both naloxone and naltrexone appear to protect nerve cells and may have direct pain-relieving activity of their own.

Low Dose Naltrexone (LDN) Downsides:

The FDA has approved a 50 mg pill of naltrexone. To our knowledge, there are no low dose naltrexone (LDN) pills available in drug stores. As a result, they must be specially prepared by a compounding pharmacy.

If a patient tries to split up a 50 mg tablet into tiny chunks it is likely the dose will be completely off. That would lead to inconsistent dosing.

Although low dose naltrexone (LDN) is being prescribed by many physicians, long-term safety studies for chronic pain patients have not been carried out. The drug seems relatively safe. Vivid dreams are one of the most common reactions. Some people may find this an acceptable trade off rather than a disturbing complication.

Low Dose Naltrexone (LDN) Upsides:

The drug should be relatively inexpensive compared to most other treatments for chronic pain. Normal dose naltrexone (50 mg tablets) cost under $40 for a months supply. A compounding pharmacy should not charge an outrageous amount for making low dose naltrexone.

LDN is being studied for a range of health conditions. Norwegian researchers reported in April, 2015, the following:

“Naltrexone in much lower doses than 50 mg has been used in Norway for the treatment of a variety of diseases, such as multiple sclerosis (MS), Crohn’s disease, fibromyalgia, cancer, inflammatory bowel disease, chronic fatigue syndrome, and amyotrophic lateral sclerosis.”

The authors note, however, that the research to date has been of very low quality and they could not determine “whether the use of naltrexone in low doses is effective or safe.”

The People’s Pharmacy Perspective:

Naltrexone was first synthesized in the early 1960s. The FDA approved it in 1984 at doses of 50 to 100 mg to help treat opioid addiction. Much more research needs to be done on low dose naltrexone (LDN) (3 to 4.5 mg) before clinicians will embrace this approach.

Given that the drug is off patent, we doubt that any pharmaceutical company will spend the money to prove safety and efficacy for chronic pain. That means the FDA is not likely to approve it for anything other than alcohol abuse or to block narcotic drugs. That’s a shame, because in doses of 1 to 4.5 mg it seems safer than many of our current pain meds.

You can learn more about the “official” use of naltrexone at this link:

Naltrexone Cuts Urge to Drink

If you have had experience with low dose naltrexone for pain, please share your story in the comment section below.