Original Study| Volume 22, ISSUE 10, P2121-2133.e24, October 2021

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An International Consensus List of Potentially Clinically Significant Drug-Drug Interactions in Older People



      We aimed to establish an explicit list of potentially clinically significant drug-drug interactions (DDIs) in people aged ≥65 years.


      A preliminary list of potentially clinically significant DDIs was compiled, based on 154 DDIs identified from literature review. Subsequently, a 2-round online Delphi survey was undertaken with a multidisciplinary expert panel. A consensus meeting and a final round were conducted to validate the final DDI list and the scope of information provided.

      Setting and Participants

      Twenty nine experts, including geriatricians and clinical pharmacists from 8 European countries.


      For each DDI, in the first 2 rounds, experts were asked to score the severity of potential harm on a 5-point Likert-type scale. DDIs were directly included on the final list if the median score was 4 (major) or 5 (catastrophic). DDIs with a median score of 3 (moderate) were discussed at a consensus meeting and included if ≥75% of participants voted for inclusion in the final round.


      Consensus was achieved on 66 potentially clinically significant DDIs (28 had a median score of 4/5 and 48 of 3 in the Delphi survey). Most concerned cardiovascular, antithrombotic, and central nervous system drugs. The final list includes information on the mechanism of interaction, harm, and management. Treatment modification is recommended for three-quarters of DDIs.

      Conclusion and Implications

      We validated a list of potentially clinically significant DDIs in older people, which can be used in clinical practice and education to support identification and management of DDIs or to assess prevalence in epidemiologic and intervention studies.


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