Reported Benefits of Low-Dose Naltrexone Appear to Be Independent of the Endogenous Opioid System Involving Proopiomelanocortin Neurons and β-Endorphin

Naltrexone 6 mg once daily versus placebo in women with fibromyalgia: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Low-dose naltrexone is used to treat fibromyalgia despite minimal evidence for its efficacy. This trial aimed to investigate whether 12-week treatment with 6 mg low-dose naltrexone was superior to placebo for reducing pain in women with fibromyalgia.

METHODS

We did a single-centre, randomised, double-blind, placebo-controlled trial in Denmark. We enrolled women aged 18-64 years who were diagnosed with fibromyalgia. Participants were randomly assigned 1:1 to receive low-dose naltrexone (6 mg) or an identical-appearing placebo, using a computerised algorithm with no stratifications applied. Participants, investigators, outcome assessors, and statistical analysts were all masked to treatment allocation. The primary outcome was change in pain intensity on an 11-point numeric rating scale from baseline to week 12, in the intention-to-treat population. Safety was assessed in participants in the intention-to-treat population who received at least one dose of their allocated intervention. This trial was registered with ClincalTrials.gov (NCT04270877) and EudraCT (2019-000702-30).

FINDINGS

We screened 158 participants for eligibility from Jan 6, 2021, to Dec 27, 2022, and 99 patients were randomly assigned to low-dose naltrexone (n=49) or placebo (n=50). The mean age was 50·6 years (SD 8·8), one (1%) of 99 participants was Arctic Asian and 98 (99%) were White. No participants were lost to follow-up. The mean change in pain intensity was -1·3 points (95% CI -1·7 to -0·8) in the low-dose naltrexone group and -0·9 (-1·4 to -0·5) in the placebo group, corresponding to a between-group difference of -0·34 (-0·95 to 0·27; p=0·27, Cohen's d 0·23). Discontinuations due to adverse events were four (8%) of 49 in the low-dose naltrexone group and three (6%) of 50 in the placebo group. 41 (84%) of 49 patients in the low-dose naltrexone group had an adverse event versus 43 (86%) of 50 in the placebo group. One serious adverse event occurred in the placebo group and no deaths occurred.

INTERPRETATION

This study did not show that treatment with low-dose naltrexone was superior to placebo in relieving pain. Our results indicate that low-dose naltrexone might improve memory problems associated with fibromyalgia, and we suggest that future trials investigate this further.

FUNDING

The Danish Rheumatism Association, Odense University Hospital, Danielsen's Foundation, and the Oak Foundation.

Low-Dose Naltrexone (LDN) for Chronic Pain at a Single Institution: A Case Series

Purpose

Low-dose naltrexone (LDN) has increased in popularity as a non-opioid medication that may decrease chronic pain symptoms. LDN is most commonly used to treat fibromyalgia, complex regional pain syndrome (CRPS), and painful diabetic neuropathy. Other studies suggest that LDN provides general symptom reduction in inflammatory conditions such as Crohn's disease and multiple sclerosis. We reviewed our experience with patients to whom we have prescribed LDN to see what types of painful conditions were most responsive to LDN in our patient population.

Patients and Methods

Charts from patients who came to the Pain Center between 2014 and 2021 were reviewed.

Results

Of the n = 137 patients who were prescribed LDN, 44% had no evidence of ever filling the prescription, and 4.4% of the responses were not charted. Of the remaining who took LDN (n = 70), 64% had some relief and were designated as 'Responders'. The most common pain diagnosis was neuropathic pain which, when added to the diagnosis of complex regional pain syndrome, accounted for 51% of responders to LDN. Patients who experienced greater than 50% pain relief from LDN were more likely to have the diagnosis of neuropathic pain or complex regional pain syndrome (p = 0.038, Fisher's Exact Test). There was a significant difference in the diagnosis of patients who responded to LDN. Patients with spondylosis were much less likely to respond to LDN when compared with other diagnoses (p = 0.00435, Chi-Square Test).

Conclusion

Patients with all types of neuropathic pain, including CRPS, were significantly more likely to have pain relief from LDN than patients with spondylosis (p=0.018). The diagnosis of spondylosis was more often associated with a lack of response to LDN than any other diagnosis. Patients may need to have a trial of several weeks before analgesic effects are seen with LDN.

Efficacy of Low-Dose Naltrexone and Predictors of Treatment Success or Discontinuation in Fibromyalgia and Other Chronic Pain Conditions: A Fourteen-Year, Enterprise-Wide Retrospective Analysis

Current pharmacologic treatments may provide limited analgesia in fibromyalgia and other chronic pain disorders. Low-dose naltrexone (LDN) has emerged as a potential analgesic option that has been minimally explored. This study aims to describe current real-world prescribing practices of LDN, to investigate if patients have a perceived benefit of LDN in treating pain symptoms and to identify predictors associated with a perceived benefit or discontinuation of LDN. We evaluated all outpatient prescriptions for LDN prescribed for any pain indication in the Mayo Clinic Enterprise from 1 January 2009 to 10 September 2022. A total of 115 patients were included in the final analysis. The patients were 86% female, had a mean age of 48 ± 16 years, and 61% of prescriptions were for fibromyalgia-related pain. The final daily dose of oral LDN ranged from 0.8 to 9.0 mg, while the most common dose was 4.5 mg once daily. Of patients who reported follow-up data, 65% reported benefit in their pain symptoms while taking LDN. Adverse effects were reported in 11 (11%) patients and 36% discontinued taking LDN by the most recent follow-up. Concomitant analgesic medications were used by 60% of patients and were not associated with perceived benefit nor discontinuation of LDN, including concomitant opioids. LDN is a relatively safe pharmacologic option that may benefit patients with chronic pain conditions and warrants further investigation in a prospective, controlled, and well-powered randomized clinical trial.

Low Dose Naltrexone for Treatment of Burning Mouth Syndrome

OBJECTIVE

The International Classification of Disease defines burning mouth syndrome (BMS) as a chronic intraoral burning sensation, with no identifiable local or systemic cause. Since current management is often unsatisfactory, the aim of this report is to describe a new treatment modality (i.e., low-dose naltrexone [LDN]).

STUDY DESIGN

A 62-year-old woman presented with the complaint of burning on the tongue of 3 years' duration. Existing comorbidities were fibromyalgia, irritable bowel syndrome, headache, and interstitial cystitis. Her reported pain intensity ranged from 2/10 (morning) to 8/10 (evening) on a numeric rating scale. With the diagnosis of BMS and hyposalivation, and in light of her current clonazepam use and fibromyalgia, a dry mouth protocol and LDN (3 mg) were prescribed.

RESULTS

After 1 month, her pain intensity decreased by 50%, with no pain upon awakening. After 2 months, the widespread pain associated with her chronic morbidities also reduced by 50%, and her headache disappeared. After adjusting LDN dose to 4.5 mg, the patient was stable at 6 months, with 50% reduction of widespread pain and 2/10 BMS pain, and no reported side effects.

CONCLUSIONS

These preliminary results suggest that LDN may be a feasible and effective treatment for BMS, especially in patients' refractory to traditional treatment.