Saw it on a documentary forever ago.
" Drug Alcohol Rev. 2006 Mar;25(2):115-21.
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atients receiving a prescription for diamorphine (heroin) in the United Kingdom.
Metrebian N1, Carnwath Z, Mott J, Carnwath T, Stimson GV, Sell L.
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Abstract
The United Kingdom is unusual internationally in that it is one of few countries able to prescribe diamorphine for the treatment of opiate dependence. Prescribing diamorphine has been part of the UK response to drug problems since the 1920s. Despite this, little is known about who receives diamorphine and how treatment is delivered. This study aims to describe the characteristics and treatment regimes of opiate-dependent drug users receiving a prescription for diamorphine in the United Kingdom in 2000, and report on their status in 2002."
https://www.ncbi.nlm.nih.gov/pubmed/16627300