In this issue of the Journal, Lintzeris and colleagues report eight patients with naltrexone implants who developed serious medical complications considered to be related to the implant (→ Unplanned admissions to two Sydney public hospitals after naltrexone implants).1 Intuitively, naltrexone is an attractive treatment for opioid dependence, as it is inexpensive, long-acting and generally well tolerated, and blocks the actions of heroin when taken orally. However, empirical support for naltrexone has been unimpressive,2-4 with research showing that poor adherence to treatment limits its effectiveness. An Australian study found that, while patients who adhered to treatment did well, only 2% were still taking the drug 3 months after conventional inpatient detoxification.5