A medication error is a failure in treatment procedures that leads to, or has the potential to lead to, patient harm (Aronson [12]). Medication administration errors occur frequently and are more likely to result in serious harm and death than other types of medication error (Westbrook et al. [366]). Direct observational studies in hospitals estimate that errors occur in 19–27% of instances when drugs are administered to patients (Westbrook et al. [366]). Studies have demonstrated that interruptions are common and that these and other distractions can increase error and accident rates relating to drug administration (Relihan et al. [298], Westbrook et al. [365]) (Box 15.4).