Perth | The hazy-eyed sheep shearer was shifting in his seat in a clinic in WA, unsure if he could do what the doctor said would save his life. A heroin user for 20 years, he was now in the depths of a detoxification treatment. "I'm all alone," he said.

In a soft voice, the doctor, George O'Neil, pleaded with the man to continue to the next stage: an implant of the drug naltrexone, a device the physician had invented and that is an emerging facet of an impassioned debate over the best way to treat addiction.