"The most widely accepted document outlining ethical standards for research at the international level is the Declaration of Helsinki [36]. There is a crucial section, paragraph 30, of the document that is pertinent to research on heroin treatment for addiction. It reads:

"'At the conclusion of the study, every patient entered into the study should be assured of access to the best proven prophylactic, diagnostic and therapeutic methods identified by the study'[37]

"The main motive for this portion of the international research guidelines is to prevent the sponsors of research trials (government, university, hospital or private) and physician collaborators from initiating research on subjects who would otherwise be unable to access the treatment offered in the research and then taking away the treatment when the research schedule is complete [36]."

Source

Small, D., Drucker, E. & Editorial for Harm Reduction Journal. Policy makers ignoring science and scientists ignoring policy: the medical ethical challenges of heroin treatment. Harm Reduct J 3, 16 (2006). doi.org/10.1186/1477-7517-3-16