Low doses of naltrexone-an inexpensive agent used for years to treat drug addiction-has helped reduce pain and fatigue in women with fibromyalgia, a debilitating disorder marked by chronic musculoskeletal pain. According to a recent study in Pain Medicine, 10 female patients were taken off their current fibromyalgia medication, then administered a placebo for two weeks, then put on naltrexone for eight weeks. The drug reduced symptoms by 30 percent compared to placebo. It also worked better for some than for others; six out of the 10 were strong respondents, with at least a 50 percent reduction in symptoms. How the drug works is not known, but researchers suggest that naltrexone may quiet a hyperactive immune system. Naltrexone has another advantage-doses of the drug cost about $40 a month. Though the study was small, it was considered scientifically sound. If more research is promising, said researchers, naltrexone may eventually compete with higher-priced fibromylagia drugs now on the market.