1) Negligence, forgetfulness or lack of attentiveness, 2) Practice beyond scope, 3) Lack of knowledge, 4) Communication errors, 5) Proper protocol not followed and 6) Disease or drug abuse. Six main categories on the system level were identified: 1) Organizational routines and culture, 2) Location of medication and look-alike medication, 3) Role overload, 4) Interruption
or distraction, 5) Pressure from patient/patient's family or staff members and 6) Lack of adequate guidelines or
information