The gains in the diacetylmorphine group were greater than those in the methadone group for drug use, psychiatric status, employment satisfaction, and social relations.
There were more serious adverse events in the diacetylmorphine group -- 51 versus 18. None of the adverse events in the methadone group was attributed to the study treatment.
The most common serious adverse events with diacetylmorphine treatment were potentially life-threatening overdoses in 10 patients and seizures in six. None of the patients died.
"Our safety data suggest that diacetylmorphine should be delivered in settings where prompt medical intervention is available," the researchers said.
Schechter added, however, that "we consider the results to show it's very, very safe."
Diacetylmorphine treatment is more expensive than methadone, Schechter said. A year of treatment costs about $6,300 to $7,300 for prescribed heroin and about $2,700 to $3,600 for methadone.
But, he said, with the cost of an untreated person with heroin addiction estimated at about $50,000 a year -- including costs associated with medical care, imprisonment, and legal proceedings -- both treatments appear highly cost-effective.
A formal cost-effectiveness analysis is ongoing, he said.
In an accompanying editorial, Virginia Berridge of the London School of Hygiene and Tropical Medicine, pointed out that European countries that have conducted similar trials have had different responses to the results, partly because of the politics and controversial nature of the treatment.
For example, she said, Switzerland and the Netherlands have begun prescribing heroin as part of their medical system, whereas Germany and Spain have balked at the idea.
"We will now wait to see what political or professional factors will support or oppose the conclusions of this study in its home territory, and whether the historical legacy of heroin will matter," she said.