Rise in Ketamine fatalities

The number of teenagers using and subsequently dying as a result of taking the party drug Ketamine has skyrocketed in recent years with more young people having fatal overdoses of the drugs than ever before.

Despite the risks, 5.8 per cent of 16-24 year old's say they have taken the drug with one in 20 admit to being regular users. 

What is the reason behind this increase?