Naltrexone (Low-Dose)
Wellness
In plain English
Naltrexone is an FDA-approved medicine that blocks opioid receptors; at full doses it is used for opioid and alcohol dependence. At much smaller "low doses" (often 1–4.5 mg), it is used off-label for chronic pain and inflammatory conditions, based on the idea that a brief receptor blockade nudges the body to make more of its own pain-relieving and anti-inflammatory signals. Evidence at low doses is early and mostly from small studies. It is generally well tolerated; vivid dreams and sleep changes are the most common complaints.
The science
Low-dose naltrexone (LDN) is thought to work differently from standard-dose opioid-receptor blockade: transient opioid receptor antagonism may upregulate endogenous opioids, and LDN may also dampen microglial activation via Toll-like receptor 4. Human evidence is limited and preliminary. In a small randomized, double-blind, placebo-controlled crossover trial in 31 women with fibromyalgia (Younger et al., 2013), 4.5 mg/day reduced pain more than placebo (28.8% vs 18.0% reduction) with improved mood and life satisfaction and good tolerability. Larger parallel-group trials are still needed to confirm efficacy across conditions. LDN should not be combined with opioid analgesics (it will block them and can precipitate withdrawal).