Objective: The purpose of this study is to investigate incidents of erroneously dispensed drugs on the assumption that the incidents stem from the similar names of the drugs.  The investigation was also conducted to prevent such dispensing incidents in the future, i.e. to search for factors that can prevent future incidents, and finally to propose a prevention plan which takes each of these factors into account.
Methods: We extracted incident cases related to generic drugs reported by pharmacies in Japan and from those cases examined those that were categorized as cases of erroneously dispensed medicine.  We used this data to categorize the difference in relationship between the drugs which were supposed to be prescribed and those which were erroneously dispensed, and to analyze the association between the “Flowchart for Avoiding Confusion Errors between Similarly Named Drugs” and the name similarity index based on this flowchart.
Results: The types of incident cases due to name similarities of generic drugs were categorized into specification mistakes and brand mistakes.  The edit of the name similarity index were especially important factors for dispensing incidents between generic drugs.
Conclusion: This study focusing on generic drugs revealed the factors that result in dispensing incidents due to name similarity.  Further empirical studies investigating the usefulness of interventions that alter the name similarity index is required.