Objective: We studied whether the statements made in the “contradicted combinations” package inserts for medications used at the Kitasato Institute Hospital, Kitasato University (henceforth, “the hospital”) and the combinations of medications listed were consistent.
Methods: We studied whether both the “contraindicated combinations” in the package insert and the listed combinations were consistent, and when they were not, we telephoned the pharmaceutical company that did not list it as a “contraindicated combination” and inquired as to the reason it was not listed as such.
Results: 1,347 pharmaceutical products were the target of this study, and among these there were 147 products that had contraindicated combinations listed in its package insert, and there were 239 combinations of contraindicated combinations.  Among the 147 products, most were cardiovascular drugs (40 drugs, 27.2%), followed by central nervous system drugs (30 drugs, 20.4%).  Among the 239 combinations, there were 47 (19.7%) combinations that were inconsistent, and the reasons for the inconsistency were 1) because they would become unusable in the event of an emergency, 2) because there are no safety issues, etc.
Conclusion: In this study, it was clear that pharmaceuticals that are inconsistent in their contraindicated drug combinations are by no means few in number.  A lack of uniformity in what is listed in the package insert regarding contraindicated combinations, which is a public document, is not something to be at all desired, and we believe it is necessary to create consistency by clarifying the standards for listing contraindicated combinations in order to avoid confusion in clinical settings in the future.