How many people in Canada use prescription opioids non-medically in general and street drug using populations?

OBJECTIVE Medical prescriptions for opioids as well as their non-medical use have increased in Canada in recent years. This study aimed to estimate the number of non-medical prescription opioid (PO) users in the general and street drug using populations in Canada. METHODS The number of non-medical PO users among the general population and the number of non-medical PO users, heroin users, or both among the street drug using population was estimated for Canada and for the most populous Canadian provinces. Different estimation methods were used: 1) the number of non-medical PO users in the Canadian general population was estimated based on Canadian availability data, and the ratio of US availability to non-medical PO use from US survey data; 2) numbers within the street drug using population were indirectly estimated based on overdose death data, and a key informants survey. Distribution and trends by usage of opioids were determined by using the multi-site Canadian OPICAN cohort data. RESULTS Between 321,000 to 914,000 non-medical PO users were estimated to exist among the general population in Canada in 2003. The estimated number of non-medical PO users, heroin users, or both among the street drug using population was about 72,000, with more individuals using nonmedical PO than heroin in 2003. Based on data from the OPICAN survey, in 2005 the majority of the street drug using population in main Canadian cities was non-medical PO users, with the exception of Vancouver and Montreal. A relative increase of 24% was observed from 2002 to 2005 in the proportion of the street drug using population who used non-medical POs only. DISCUSSION There is an urgent need to further assess the extent and patterns of non-medical prescription opioid use, related problems and drug distribution channels in Canada.