Lack of knowledge.
D000700:Analgesics; D004335:Drug and Narcotic Control; D006266:Health Education; D003932:Heroin; D006801:Humans; D009021:Morphine Dependence; D010880:Piperidines; D019966:Substance-Related Disorders / Q000517:prevention & control*; D006113:United Kingdom; D014944:World Health Organization
D000700:Analgesics; D010880:Piperidines; D003932:Heroin