Back in 2015, the then-government announced that the first supervised drug injection centre in the country would open within two years.The centres - known as medically supervised injecting facilities (MSIFs) - provide drug addicts with a safer, sterile environment in which to inject heroin, cocaine or others drugs under the supervision of a medical professional. Users source their own drugs and inject themselves in booths in the centreIt's more than four years since that announcement was made. It was included in the Programme for Government, the enabling legislation was passed - and yet the first centre still hasn't opened, currently stuck in planning permission limbo. Why has it taken this long?In this episode of The Explainer, TheJournal.ie's Cormac Fitzgerald and Christine Bohan delve into the current situation around supervised drug injection centres in Ireland, how Irish politicians have lagged behind on drug policy, the concerns expressed around opening the pilot scheme in Dublin city centre, as well as the facts behind their effectiveness.