Low Dose Naltrexone: What It Is, How It Works, What We Know
The naltrexone tablet a pharmacy stocks is 50 mg. The dose prescribers use as low dose naltrexone is a small fraction of that. That gap is the entire reason LDN exists as a compounded medication, and it is the right place to start understanding it.
Why LDN has to be compounded
Naltrexone is FDA approved at 50 mg for opioid and alcohol use disorders. Low dose naltrexone refers to doses in the low single digit milligram range, used off label for other purposes. No manufacturer makes a product at those strengths.
That is not a marketing angle. It is a manufacturing fact, and it is the whole reason a prescriber sends an LDN prescription to a compounding pharmacy rather than writing for a commercial product.
Splitting or crushing a 50 mg tablet at home does not solve it. The amounts involved are far too small to divide accurately by hand, and doing so gives an unknown dose. A compounded capsule delivers the strength written on the prescription.
Compounding exists to serve a patient specific need that no manufactured product meets. LDN is one of the clearest examples of that principle in practice, which is different from saying it is proven to work.
How it is thought to work
The leading explanation is that a brief, low dose blockade of opioid receptors prompts the body to respond by increasing its own endorphin activity. At 50 mg naltrexone blocks opioid receptors continuously. At a much smaller dose the blockade is short lived, and the theory is that the rebound afterward is the point.
A second proposed mechanism involves glial cells, the immune cells of the nervous system. Researchers have suggested that low dose naltrexone acts on Toll like receptor 4 on these cells and dampens neuroinflammation, which would explain interest in conditions where inflammation in the nervous system is thought to contribute.
Both explanations are described in the literature as proposed and under investigation rather than established. A plausible mechanism is a reason to study something. It is not evidence that it works.
What the evidence actually shows
Reviews consistently support that low dose naltrexone is well tolerated. Evidence that it is effective is thinner and points in more than one direction. Both halves of that sentence belong in any honest description.
| Study | What it looked at | What it found |
|---|---|---|
| Younger et al. 2013 | Small randomized crossover trial in fibromyalgia | Reported reduction in daily pain compared with placebo in a small sample |
| Bruun et al. 2024 | Randomized placebo controlled trial in women with fibromyalgia, published in Lancet Rheumatology | Did not meet its primary outcome |
| Partridge et al. 2023 | Systematic review of LDN in fibromyalgia | Described the evidence as limited, with small studies and mostly subjective outcomes |
| Toljan and Vrooman 2018 | Review of therapeutic use across conditions | Safety and tolerability supported. Efficacy data more limited. |
LDN has also been studied in multiple sclerosis and Crohn's disease, with the same pattern. Tolerability holds up. Efficacy findings vary by study, and many rely on self reported outcomes such as pain scores and quality of life, which are exactly the measures most affected by expectation.
Low dose naltrexone is not FDA approved for any of these conditions and is not a proven treatment for them.
What the literature reports about dosing
Published studies of LDN have generally used doses in the range of roughly 1.5 to 4.5 mg, most often taken once daily, with several protocols starting lower and increasing over weeks. That describes what researchers have used. It is not a dosing recommendation, and this page is not a protocol.
Some studies have used bedtime dosing, linked to the proposed mechanism around the body's own endorphin activity overnight. Others have not. The literature does not establish a single correct schedule.
Your dose, your schedule and whether LDN is appropriate for you at all are decisions for your prescriber, made after evaluating your situation. Do not use the ranges above to start, adjust or stop a medication. A compounding pharmacy prepares what is prescribed and does not set the dose.
What the prescribing conversation involves
Because LDN is off label and the evidence is mixed, the conversation with a prescriber matters more than it would for a routine prescription. These are the points worth covering before starting.
What specifically are we hoping this does for me? What does the evidence show for that use, honestly? Are there approved treatments we should try first? Do any of my current medications rule this out? How long before we reassess, and what would make us stop?
- Pharmacy
- Mixwell Compounding Pharmacy
- Address
- 13788 Roswell Ave, Ste 158, Chino, CA 91710
- Phone
- (909) 378-7301
- Fax
- (909) 378-7071
- info@mixwellpharmacy.com
The question about current medications matters most. Naltrexone blocks opioid receptors, so it interacts directly with opioid containing medications. Tell your prescriber about everything you take, including anything prescribed for pain.
How you and your prescriber tell whether it is working
There is no blood test, wearable metric or biomarker that shows whether low dose naltrexone is working. Assessment is based on how you feel over time, tracked against what you and your prescriber agreed to watch before starting.
That makes two things important. Agree on what you are measuring before you begin, because deciding afterward invites reading meaning into normal variation. And agree on a timeframe and a stopping point, so that continuing is a decision rather than a default.
Reasonable to track
- A specific symptom you and your prescriber named at the start
- A simple daily rating rather than an impression at the end of a month
- Function, such as what you can do that you could not before
- Any new symptom or side effect
Worth being cautious about
- Treating a good week as proof, since most conditions fluctuate
- Wearable or biomarker data, none of which is validated for this
- Adjusting anything yourself between appointments
- Continuing indefinitely without a review
Conditions where LDN is used tend to wax and wane on their own. That is exactly why placebo groups in these trials often improve, and why an individual impression of benefit is genuinely hard to interpret.
Prescriber question about capsule strengths, titration sets or filler conscious preparation?
Call (909) 378-7301Side effects to know about
Low dose naltrexone is generally described as well tolerated in the published literature, but it is a prescription medication with real effects.
The most commonly reported effects are vivid dreams or disturbed sleep, headache, and gastrointestinal upset including nausea. Naltrexone blocks opioid receptors, so it can interfere with opioid containing medications and can precipitate withdrawal in someone who is opioid dependent. Tell your prescriber about every medication you take, including pain medications, and tell any other treating clinician that you are taking it, particularly before a procedure where opioid pain relief might be used. Naltrexone labeling includes cautions relating to liver function, and your prescriber decides whether any monitoring is appropriate for you. This list is not complete. Report any new symptom to your prescriber, and do not start, stop or change a dose without speaking with them.
Sending a prescription to Mixwell
State the strength per capsule, the quantity and the directions on a patient specific prescription. Note if you want more than one strength prepared for a titration schedule.
- Write the strength per capsule and the number of capsules to dispense.
- Note if you want multiple strengths prepared so the patient can step up or down.
- Note any excipient preferences, such as a dye free capsule shell.
- Call (909) 378-7301 to confirm the formulation and current turnaround time.
Serving prescribers and patients in California
Mixwell Compounding Pharmacy is located in Chino, CA and works with integrative medicine, rheumatology, pain and primary care prescribers across the Inland Empire, Los Angeles County and Orange County. Patients can collect their preparation at the Chino pharmacy, and delivery is available across California.
- Chino
- Chino Hills
- Ontario
- Rancho Cucamonga
- Upland
- Pomona
- Diamond Bar
- Corona
- Riverside
- Eastvale
- Brea
- Fullerton
Common questions
Why can I not just buy low dose naltrexone?
Naltrexone is FDA approved at 50 mg. Low dose naltrexone uses doses in the low single digit milligram range, and no manufacturer makes a product at those strengths. It must be compounded to the strength a prescriber specifies, under a valid prescription.
Can I just split a 50 mg tablet?
No. The amounts involved are far too small to divide accurately by hand, and doing so gives an unknown dose. Talk to your prescriber rather than attempting to divide a tablet.
Does low dose naltrexone work?
The evidence is mixed. Reviews consistently support that it is well tolerated, but efficacy findings vary by study and many rely on self reported outcomes. A randomized placebo controlled trial in fibromyalgia published in Lancet Rheumatology in 2024 did not meet its primary outcome. LDN is not FDA approved or proven for the conditions it has been studied in.
How will I know if it is working?
There is no blood test, wearable metric or biomarker validated for this. Assessment is based on how you feel over time. Agree with your prescriber before starting on what you will track and when you will review it, since the conditions LDN is used for tend to fluctuate on their own.
Does it interact with pain medication?
Yes. Naltrexone blocks opioid receptors, so it can interfere with opioid containing medications and can precipitate withdrawal in someone who is opioid dependent. Tell your prescriber about every medication you take, and tell any other treating clinician that you are taking it.
Is low dose naltrexone FDA approved?
Naltrexone is FDA approved at 50 mg for opioid and alcohol use disorders. Low dose naltrexone is used off label and is not FDA approved at those doses. Compounded preparations are not FDA approved and require a valid prescription.
Does Mixwell accept insurance?
Mixwell does not accept insurance. Call (909) 378-7301 to discuss current pricing.
Key Takeaways
- Naltrexone is FDA approved at 50 mg, and low dose naltrexone uses a small fraction of that, which is why no manufactured product exists and compounding is required.
- The proposed mechanisms involve a rebound in the body's own endorphin activity and an effect on glial cells, both described in the literature as under investigation rather than established.
- Reviews consistently support that LDN is well tolerated, while efficacy findings vary and a 2024 randomized trial in fibromyalgia did not meet its primary outcome.
- No blood test, wearable metric or biomarker is validated for assessing LDN response, so agree with your prescriber in advance on what to track and when to review.
- Compounded preparations are not FDA approved, require a valid prescription, and naltrexone interacts directly with opioid containing medications.
Sources
- Younger J, Noor N, McCue R, Mackey S. Low dose naltrexone for the treatment of fibromyalgia: findings of a small, randomized, double blind, placebo controlled, counterbalanced, crossover trial assessing daily pain levels. Arthritis and Rheumatism. 2013;65(2):529-538.
- Bruun KD, et al. Naltrexone 6 mg once daily versus placebo in women with fibromyalgia: a randomised, double blind, placebo controlled trial. Lancet Rheumatology. 2024;6(1):e31-e39.
- Partridge S, et al. A systematic literature review on the clinical efficacy of low dose naltrexone in fibromyalgia. Heliyon. 2023;9(5):e15638.
- Toljan K, Vrooman B. Low dose naltrexone, a review of therapeutic utilization. Medical Sciences. 2018;6(4):82.
- U.S. Food and Drug Administration. Naltrexone hydrochloride tablets, prescribing information.
- U.S. Food and Drug Administration. Compounding and the FD&C Act, Section 503A.