 Some proponents of low-dose naltrexone have brought forth unproven claims about its efficacy in treating a wide range of diseases, including cancer, Myalgic Encephalomyelitis / Chronic Fatigue Syndrome and HIV/AIDS.Low-dose naltrexone organizations have promoted its use on their webpages.Naltrexone and its active metabolite 6-β-naltrexol are competitive antagonists at μ-opioid and κ-opioid receptors, and to a lesser extent at δ-opioid receptors.