Japan is unique among Asian countries in that it requires inclusion of substantial domestic clinical trial data in new drug application data packages. Some question the need for this and call for globalization of approved doses. The current study examines international differences in maximum daily dose of drugs approved in Japan between 2001 and 2007, and for all cardiovascular system (CVS) and central nervous system (CNS) drugs marketed in Japan. For 32% of the drugs approved in Japan between 2001 and 2007, the maximum recommended dose in the United States was > or =2 times higher than the maximum dose approved in Japan. Dose differences were rare for antitumor and antiviral drugs and also for priority-review and orphan drugs. Of all the price-listed CVS drugs currently available in Japan, 65% had maximum doses that were > or =2 times higher in the Netherlands than in Japan; similarly, 57% of the drugs had maximum doses that were > or =2 times higher in the United States than in Japan. For CNS drugs, these figures were 32% (the Netherlands) and 29% (United States). These results underscore the necessity to carry out quantitative analyses to determine the causes of these differences.

The occurrence of SRRAs was associated with the accumulation of both foreign and domestic postmarketing evidence rather than with clinical trial data upon launch. Considering the paradigm shift to simultaneous global drug development and filing for regulatory approval, this study indicates the importance of intensive data collection in the early postmarketing phase and use of safety information in early markets. However, even if we would be sufficiently cautious about safety risks of new drugs, a population that enjoys first-in-class drugs probably has to bear the risks.

Although it is well known that there are differences in approved doses between Japan and the United States, there has been no comprehensive research into the causes thereof. This study furthers the discussion of our previous investigation in 2010, with particular focus on pharmaceutical industry strategy and regulatory policy, among drugs approved in Japan between 2001 and 2009. Dose differences were observed in 73 of 190 drugs. Non-Japanese firms were more likely to have a similar dose approved between Japan and the United States, the association being more pronounced when limiting the analysis to drugs for which a Japanese dose-finding study was not conducted. Furthermore, dose differences were less frequent when non-Japanese efficacy data were included in the application data package. No relation between potential intrinsic ethnic difference and dose difference could be identified. The results suggest that the pathway of drug development is more strongly associated with dose difference than are drug characteristics.

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