Purpose It is important to make the most up‐to‐date drug safety information available to the public in a timely manner so that health care professionals and patients can consider the information. The aim of the present study was to investigate the consistency and simultaneity of safety related updates in product labeling in Japan and the United States. Methods New safety label changes that were made for new drugs approved concurrently both in Japan and the United States in the recent 5 years were identified and reviewed for concordance and time lag analysis. Factors associated with the time lag were also investigated. Results Despite similar medical practices, population health and regulation in the countries, a low level of concordance (40/115, 34.8%) in the decision of labeling change was found in 31 new active substances. Only 3/40 (7.5%) of the concordant changes were made simultaneously. Labeling change orders issued by regulators and domestic postmarketing adverse event reports were associated with a significant difference in the timing of labeling change between the countries. Conclusions We found a low level of concordance between regulators in the decision of labeling changes and the timeliness of the changes. The low concordance and time lag highlighted the need for further international collaboration between regulators and industry and greater transparency in the decision‐making process for the label change.

Purpose Scientific information in the drug labeling is expected to be the most up-to-date and consistent information across countries where medicine is approved. The objective of the present study is to investigate the consistency of safety-related information on product labeling for novel therapeutics concurrently approved in Japan and the US. Methods Safety information at the time of initial approval of new drugs approved concurrently both in Japan and the US in the recent 7 years were identified and reviewed for concordance. Factors associated with the discordance were also investigated. Results Despite the similar medical practices, population health, and regulation in Japan and the US, the level of concordance of safety information found in the drug labeling of 45 new active substances was low (20.4%). The development strategy of the drugs and having the same MAH were significantly associated with the concordance rate. The mean concordance rate among the 9 drugs with Black Box Warning in both countries was also low (32.9%). Conclusions We found a low level of concordance between Japan and the US even when related to clinically important information raised by Black Box Warnings. The low concordance rate highlighted the need for a greater transparency in decision-making processes about the safety information in a drug labeling by both industry and regulators to take appropriate countermeasures against the discordance.