The U.S. Food and Drug Administration approved a drug-emitting arm implant to treat addiction to heroin and other opioids, providing a new tool against a condition that has proved extraordinarily difficult to manage.

Some addiction experts said the implant could offer a more reliable way to keep addicts on their medication. But like all drugs meant to treat drug addiction, the device could face opposition from those who embrace the total-sobriety approach to treatment long advocated by 12-step programs.

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