[Safe injection rooms and police crackdowns in areas with heavy drug dealing. Evaluation by counting discarded syringes collected from the public space].

The evolution of drug injection in public places is analysed using as indicator the number of syringes collected from public spaces, evaluating as well the influence of public health harm reduction interventions and of police actions, with a before and after quasi experimental study. Monthly syringe counts on the semester before and after each intervention were compared both in the involved district and in the city as a whole, using the U and z tests with a 95% confidence level. The average number of collected syringes drops from 13.132 in 2004 to 3.190 in 2012. Comparing indicators before and after health and police interventions, the opening of a facility with a supervised drug consumption room in the inner city was associated with a huge reduction in the number of abandoned syringes in the city, while its number did not rise in the district where the facility was located. The subsequent opening of another drug consumption room did not have a significant impact in collected syringes in the area. Some police interventions in 2005-2006 and 2011 had a significant impact in the indicators of the involved districts, while others did not. Harm reduction programs might have a favourable impact on drug injection in public spaces and related syringe presence. Some police interventions appear to have an impact while others do not or just have a modest local and temporary effect.