Polypharmacy in three different spontaneous adverse drug event databases

Polypharmacy has become a major problem in medical care worldwide, including in Japan. The purpose of this study was to investigate the current situation of polypharmacy using different spontaneous adverse drug event report databases.A retrospective data analysis was performed using reports from 2007 to 2015 from three different spontaneous adverse drug event report databases: the Japanese Adverse Drug Event Report (JADER) constructed by the Pharmaceuticals and Medical Devices Agency in Japan, the US Food and Drug Administration (FDA) Adverse Drug Event Reporting System (FAERS) constructed by the FDA in the United States, and the Canada Vigilance Adverse Reaction Online Database (CVARD) constructed by the government of Canada. Polypharmacy trends during the study period were investigated.The mean numbers of drugs per report in the JADER, FAERS, and CVARD databases during the study period were 6.62, 3.76, and 3.44, respectively. The mean number of drugs per report increased with age in all three databases, with a peak at ages 70 - 79 years in all three databases (7.0 drugs for JADER, 4.7 drugs for FAERS, and 4.2 drugs for CVARD).Adverse event reports were more likely to develop in the patients treated through polypharmacy. Polypharmacy in Japan should be improved to prevent adverse events. Additionally, the patients aged ≥ 80 years tended to develop adverse events even if the number of prescribed drugs was relatively small. Therefore, polypharmacy should be noted in these patients to prevent adverse events.