Objective: Similarity of drug names is one factor of dispensing incidents.  The aim of this study was to survey the relation between sensual similarities of drug names and the occurrence of taking errors for pharmacists who actually prepare medicine.
Methods: A pair of drugs (15 incident pairs and 104 control pairs) was displayed on a computer screen at random.  The subject’s task was to determine the sensual similarity of them.  Thirteen pharmacists who prepared these pairs and caused their incidents participated in the experiment.
Results: The result showed that the sensual similarity of drug names of incident pairs was found to be highly significant in comparison to one of the control pairs [p=0.026].  However, the similarity in incident pairs is not necessarily high.  It was suggested that the similarity of drug name was not the only factor of taking error.  Multiple linear regression analyses of the sensual similarity in control pairs were performed, in which 10 variables were reported as quantitative indicators of similarity of drug name and were able to be measured on the internet.  The correlation was good [R²=0.828].  However, this regression model was not useful when adjusting to incident pairs.  In incident pairs, the similarity value calculated by the regression model was lower than the measured sensual similarity.
Conclusion: The result suggested that measured sensual similarity includes other risk factors of taking error, such as appearance similarity and/or efficacy similarity and/or short distance arrangement.  It seemed that the pharmacist’s ability complicated the factor of taking error.