The similarity of drug names is one of the common causes of medication error. In Japan, similarity evaluation is performed prior to approval of new drugs in order to avoid potential confusion. However, existing indices do not take account of the difference between characters that contain voiced or semi-voiced and unvoiced sounds, so it is not clear whether such sounds influence the subjective similarity of drug names. Thus, we performed a cognitive psychological experiment to investigate this issue, using participants who had not received any education in medicine, nursing, or pharmacy. An analogue scale questionnaire was used to evaluate the subjective similarity of the names of drug pairs. Drug pairs for the main analysis were prepared by matching the first 0 to 3 characters, and then varying the difference in the number of voiced and semi-voiced characters from 0 to 3 in these matched characters. By means of this procedure, the drug pairs were classified into a total of 10 groups. Then, a total of 60 drug pairs were created by assigning 6 drugs to each group. The subjective similarity tended to increase with increasing number of common characters among the first three characters. When classified according to the number of these common characters, the subjective similarity was significantly decreased when voiced or semi-voiced sounds were present, as compared with when they were absent. These results indicate that a new drug name similarity index that takes account of voiced and semi-voiced sound differences should be developed to minimize medication errors.
Keywords: cognitive psychological experiment; confusing drug name; semi-voiced sound; subjective similarity; voiced sound.