A drug called naltrexone is used to treat heroin addicts as it blocks the receptors heroin uses to generate its effect. Unfortunately the effectiveness of naltrexone can be limited as people often forget to take it orally. One way round this problem is to use a long-lasting injection which delivers the drug gradually into the bloodstream. A team of researchers from Australia compared the effectiveness of a long-lasting injection with that of oral naltrexone in a study of 70 heroin addicts. As well as comparing the injections to oral naltrexone the researchers also compared both treatments to a placebo. The study found that the implant led to higher levels of the drug in people's bloodstreams, fewer people returning to heroin use and people going longer before relapsing.
Hulse, Gary K. ... [et al] - Improving clinical outcomes in treating heroin dependence Archives of General Psychiatry October 2009, 66(10), 1108-1115