Table 1. Characteristics of the hospitals involved in this study.

Characteristics	Korea	Belgium	UK	USA
Period of time coverage	4 mon (Sep.–Dec. 2014)	1 yr (Jan.–Dec. 2011)	1 yr (Jan.–Dec. 2011)	3 yr (2009–2011)
Hospital type	Tertiary teaching hospital	Tertiary teaching hospital	Tertiary teaching hospital	Tertiary teaching hospital
Clinical setting	Inpatient and outpatient	Inpatient	Inpatient	Outpatient
DDI rule knowledge base	National rules	Commercial rules	Self-developed rules	Self-developed rules
Priority system for DDI rules	No levels (all rules are interruptive)	6 levels (trigger alerts only for level 1 and 2)	2 levels (hard stop, & interruptive)	3 levels (hard stop, interruptive, & non-interrupted)

DDI = drug–drug interaction.