Recent research conducted in Canada has shown that giving heroin to heroin abusers who are not successful in conventional treatment has allowed for better treatment outcomes than continuing the failed treatment approach. The researchers followed 226 heroin addicts who had been abusing heroin for many years. These individuals had failed to improve by following conventional treatment. After one year 88% of the addicts who were given heroin were still in the study, compared to 54% of the addicts in the control group who had received methadone (one of the most popular treatment regimens). One caveat, those take heroin injections suffered more side effects including serious overdoses.
The U.S. government estimates that there are approximately 663,000 heroin abusers in the United States with approximately 15% of those individuals considered candidates for heroin prescription treatment. This can't happen overnight though. In the U.S. heroin is classified as a Schedule I substance which defines it as a substance that has a high potential for abuse and serves no legitimate medical purpose.
So we won't see this treatment modality anytime soon in the United States.
ref: NY Times August 20, 2009