Whether concomitant drug abuse leads to an increased number of deaths was scientifically analysed in Sheffield, UK.  The researchers wanted to find out whether concomitant drug abuse (. an opiate plus another drug of misuse) leads to an increased number of acute accidental opiate-related deaths. The authors showed that at least in the Sheffield area, intravenous (IV) administration of an opiate is the most consistent factor associated with drug abuse deaths. The co-administration of a concomitant drug of misuse appeared to be a feature rather than a risk factor per se in such deaths.