 Naltrexone is an opioid antagonist that is FDA approved in an oral daily dose of 50 mg to prevent recidivism in alcoholics. At much lower doses of 4 - 4.5 mg daily, however, it has been shown in small, blinded, randomized trials to improve pain in fibromyalgia, gastrointestinal symptoms in Crohns disease, and quality of life in multiple sclerosis. The only other published data are case reports in complex regional pain syndrome, low back pain, and scleroderma. However, advocacy of low-dose naltrexone LDN by internet-based MDs and patients is high, and since LDN can be prescribed off-label, its use greatly exceeds what is justified by evidence. The drug can be prescribed only via compounding pharmacies, so its use costs a patient 40month. 