Differences between Japan and the United States in dosages of drugs recently approved in Japan.

The internationalization of clinical and regulatory guidelines and disease treatment and the globalization of the pharmaceutical industry have led drug development strategies in Japan to shift from bridging studies to multinational trials. However, the current standard for adequate dose-finding processes may sometimes complicate the timely participation of Japan in these multinational trials. The objective of this study is to investigate different factors that might influence dosage selection in Japan. Approved drug dosages in Japan and the United States during the period 2003-2008 were compared and assessed across different therapeutic areas and approval timings. Factors such as company type and daily dosage indication were demonstrated to have a statistically significant relationship with different dosages in Japan and the United States. Anticancer, antiviral, and enzyme drugs showed similar dosages in the 2 regions, whereas neurological drugs were observed to undergo more careful dosage-finding processes, resulting in the approval of generally lower doses in Japan. A broader analysis is needed for detailed assessment. The findings in this study serve as an initial review to identify important factors that should be considered before planning global drug development.