Key points:
- A new analysis has identified nearly 4,000 drug pairings that are associated with more frequent dosage adjustments when prescribed together.
- The study is based on data from over 1 million patients and 77,249 total drug pairings.
- Almost 700 medications have not been previously shown to potentially cause harmful drug interactions.
With many chronic diseases, patients are prescribed a combination of medications to keep all levels and vitals within normal range, a practice called polypharmacy.
In the past, polypharmacy research has typically focused on the number and type of drugs a patient receives. However, a new study has found that the dosage of each drug may also influence interactions and health outcomes.
Researchers at University of Copenhagen analyzed data from the electronic health records of more than 1 million patients admitted as inpatients in Danish hospitals from 2008 to 2016. They used Bayesian inference—a common statistical method—to identify drug pairings associated with more frequent adjustments to the dosage of the drugs.
Out of 77,249 total drug pairings, 3,993 were associated with more frequent dosage adjustments when given together. Further analysis showed that, of the pairs associated with more frequent dosage adjustments, 2,412 were also associated with hospital readmission, mortality, or longer hospital stays, and 308 were associated with worsened kidney function.
Many of the drug pairs associated with dosage adjustments have already been linked by previous research to potential harmful drug interactions. However, 694 have not, and while this study does not prove any cause-effect relationships, the authors say that some of these drug pairings may involve previously undiscovered interactions. These are often given to fewer patients and therefore harder to detect in small scale studies—contrary to the 185 million treatment episodes used in this study. Future research will be needed to explore that possibility.
Overall, these findings help deepen understanding of links between drug dosage and polypharmacy, and could help guide future evaluation of drug interactions and efforts to reduce the risks of polypharmacy for patients.