So far, doctors have had little hope of treating the 10 percent or more of heroin users who don't respond to methadone, the standard anti-addiction medication. Fueled by drug cravings, those users often spiral downward into crime and diseases spread by dirty needles and unhealthy living.

Short of actually getting addicts off the drug, heroin clinics can at least get them off the streets.

What we are dealing with here is a very severe group of heroin addicts, where all of the treatments have been tried and have failed, said Dr. John Strang, an addiction expert at King's College London, who led the new study.

They are like oil tankers heading for disaster, he added. The question we were asking was, 'Can we change the trajectory of these tankers?' And the answer was, 'Yes we can.'

To test how prescription heroin would work for this group, Strang and his colleagues invited 127 addicts into supervised injecting clinics. The researchers then randomly chose who would get heroin, injected methadone or typical swallowed methadone.

After six months, 101 addicts had stuck with their treatment. More than two-thirds of those on heroin had no sign of street heroin in their urine at least half the time they were tested; before the study, they had been using the street drug almost every day.

In comparison, less than a third of the addicts on either type of methadone had a similar number of clean tests.

At this point, said Strang, several users have continued in the program for more than two years. He did not have exact numbers, but told Reuters Health that some had been able to get jobs and reconnect with their families.

These sorts of changes are typical of what we are seeing, he said. People are not only physically getting better, but they're getting back into society.

The researchers had to treat about two addicts for each one who get off of street drugs at least half of the time.

An estimated 3.7 million people in the US have used heroin at some point in their lives, according to the National Institute on Drug Abuse. Of current users, studies suggest that some 200,000 spend time in jails each year.

The most common drug treatment for heroin users is methadone, a synthetic drug related to heroin. Although methadone decreases the cravings for its chemical cousin, it doesn't produce the same high, according to experts. This could help explain why a substantial proportion of addicts in treatment backslide.

Before the new study, a handful of other reports had indicated that prescription heroin could help these people. But the scientific community wasn't completely convinced, in part because earlier urine tests weren't very sophisticated.

What this study did is that it used a very novel urine test that can differentiate between street heroin and prescription heroin, said Thomas Kerr, director of the Urban Health Research Initiative at the University of British Columbia in Vancouver, Canada. Street heroin contains papaverine, a remnant of the opium poppy that can be detected in the urine.

Now, he said, the evidence is quite clear that there is a place for prescription heroin for the treatment of individuals who do not respond to methadone.

Only a few European countries prescribe heroin to addicts, and in the US this practice has been illegal since before World War I.

Many argue that giving addicts more of the substance they abuse makes little sense, and would be like treating an alcoholic with whiskey.

But Kerr said that analogy wasn't apt. I would argue it's completely immoral and unethical to fail to treat those individuals and to allow them to suffer and allow the community around them to suffer, Kerr said.

Strang said he supported the UK Government's 2008 Drug Strategy, which proposes rolling out prescription heroin.

Now that we know that it works, we have to debate whether or not we should use it, he said.

Medicine