Off-Label, Low-Dose Naltrexone for Refractory Chronic Low Back Pain

Extract

Dear Editor,

Naltrexone is a long-acting, orally administered, potent, competitive opioid antagonist used in treatment of narcotic addiction at a dose range of 20–80 mg/day [1]. More recently, the drug has been used at a dose range of 1–5 mg per day to treat chronic pain and autoimmune disorders. Naltrexone used in this dose range is typically referred to as low-dose naltrexone (LDN) [2]. Pilot trials of LDN in Crohn's disease [3], multiple sclerosis [4], cancer-related pain [5], and fibromyalgia [6] have recently been conducted. Here, we report a case in which LDN resulted in a dramatic improvement in paraspinal pain.

The patient was a 35-year-old male who had experienced nonspecific left-side chronic low back pain for 2 years. The medical history was unremarkable, and treatment with short-acting opioid analgesics (tramadol), nonsteroidal anti-inflammatory drugs (diclofenac and piroxicam), tricylclic antidepressant (amitrypitine), anti-epileptics (pregabalin and duloxetine), physical therapy, trigger point injection, and three injections of corticosteroid (prednisolone acetate 40 mg/mL [two epidural and one facet joint injections]) were not effective despite satisfactory self-reported compliance. Visual analog scale (VAS, 0–100 points) for pain was 90–100 most of the time, and interfered with almost all the daily activities. His score on the Modified Oswestry's Disability Questionnaire (MODQ) was 65–70% at the time of presentation to clinic, at which time he had been on medical leave for around 12 weeks. No other remarkable findings were noted on physical examination. Laboratory investigations performed at baseline, including C-reactive protein level and complete blood cell count, were within normal limits. Lumbar spine plain radiographs and computed tomography scans were normal, and lumbar magnetic resonance imaging (December 2011) revealed diffuse posterior bulge and right posterolateral disc perfusion at L5–S1 causing bilateral (right > left) compression of neural foramina, whereas the pain was on the left (Figure ⁰⁰⁰¹).