Analysis of patients’ request to switch from a generic drug to the original drug in external prescriptions

BACKGROUND: Generic drugs are heavily promoted in Japan. The aim of this retrospective single-center study was to clarify whether the frequency and reason that patients request a switch from a generic drug to the original drug differ according to therapeutic category and dosage form. METHODS: This study was performed at Chiba University Hospital. Prescription inquiries about 121 generic drugs from community pharmacies over a 3-year period (from July 2014 to June 2017) were analyzed. RESULTS: Approximately 30% of the requests were related to the efficacy, safety, and comfort of the generic drug. The most cited motive was “patient’s desire with no reason given” at 44.5%. According to multiple logistic regression analysis, therapeutic categories and dosage forms were associated with the requests. The median request frequency differed according to therapeutic category and dosage form. The frequency was highest for “agents affecting the central nervous system” and “tablets and capsules”, respectively. Among the therapeutic categories, “agents affecting the central nervous system” had the highest median number of requests related to “decreased effectiveness”; “cardiovascular agents” had the highest median number of requests related to “physician’s instruction”; and “agents for the epidermis” had the highest median number of requests related to “uncomfortable to use”. Among dosage forms, the odds ratio for patients’ original drug request for “liniment and patch” was about 1.5 times that for “tablets and capsules”. “Liniment and patch” had the highest median frequency of requests related to “decreased effectiveness”, “uncomfortable to use”, and “patient’s desire with no reason given”. CONCLUSIONS: The request frequency and reason differed according to therapeutic category and dosage form. Pharmacists should advise each patient properly about the choice and switching of drug brands, taking into account the therapeutic category and dosage form, especially liniments and patches.