Low Dose Naltrexone for Fibromyalgia Pain - Use it or Lose it? Medscape recently reviewed off-label use of low dose naltrexone (LDN) in fibromyalgia (FM) and found it is deemed effective by some clinicians and patients, but 1) there is no FDA indication for LDN use in FM and 2) https://t.co/RgRRHU9ZRo