Benzodiazepine

Although the number of people reporting benzodiazepine as their main problem drug is low at 167 in 2008, that figure represents a 120% increase since 2003. Almost all deaths where benzodiazepine was implicated involved the use of more than one substance, most frequently alcohol and opiates...

Source: http://www.thejournal.ie/increase-in-number-dying-from-sedative-abuse-2010-12/