Estimation of total prescription weights of active pharmaceutical ingredients in human medicines based on a public database for environmental risk assessment in Japan.

The distribution of active pharmaceutical ingredients (APIs) in prescription medicines for human consumption in Japan was estimated using the public database of the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB). From the latest NDB, 2058 APIs were identified, and the prescription weight exceeded 1 tonne/year for 711 APIs. Of these, 298 APIs were selected for further analysis after removing 413 APIs that were not covered by current environmental risk assessment (ERA) directives or were combination products. Among the 298 APIs, 43 were relatively newly branded APIs that have been available on the Japanese market since 2001 or later and have no generic drugs, and only 5 of the branded APIs are used by more than 1% of the population. When prescription data from the 47 prefectures in Japan were analyzed, prescription weights for 257 of the 298 APIs were the highest in Tokyo, probably because of its large population. Though it has both advantages and limitations, this novel method based on a non-profit public database can provide a transparent, unbiased and cost-effective solution for the estimation of the environmental exposure of generic and branded human medicines distributed with prescriptions in Japan.