Today, I reviewed and link to Emergency Medicine Cases’ Ep 184 Must Know Drug Interactions in Emergency Medicine*. Continue at 35:00.
*Helman, A. Himmel, W. Juurlink, D. Must Know Drug Interactions in Emergency Medicine. Emergency Medicine Cases. June, 2023. https://emergencymedicinecases.com/drug-interactions-emergency-medicine. Accessed September 16, 2023
All that follows is from the above resource.
Drug interaction-related morbidity and mortality is highly under-recognized in Emergency Medicine. Patients who present with altered level of awareness, delirium, syncope and falls are often admitted to hospital without a definitive diagnosis; and only later is it recognized that a drug interaction was at play. Thirty percent of ED patients have at least one drug related problem contributing to their ED visit, which includes adverse drug reactions and subtherapeutic dosing. More than 1 in 9 ED visits are due to drug related adverse events, and many of these drug-related adverse events are due to drug interactions which are almost entirely preventable. In this EM Cases podcast Dr. David Juulink, Dr. Walter Himmel and Anton delve into some common presentations that require having drug interactions in the differential diagnosis, which combinations of drugs to avoid when ordering in the ED and when prescribing for outpatient therapy from the ED, high risk patients for drug interactions and the top 3 drug categories to be aware of when it comes to drug interactions…
First, we need to understand the difference between pharmacokinetics and pharmacodynamics
All drug interactions can be split into pharmacokinetic and pharmacodynamic interactions.
Pharmacokinetics can be thought of simply as what a body does to the drug. Drugs are absorbed, distributed, metabolized, and excreted. Anything that disturbs these processes can change the serum drug level.
Pharmacodynamics can be thought of simply as the effect of the drug on the body. For example, the synergistic impact that two drugs might have on prolonging the QT interval.
When to consider drug interactions in the differential diagnosis
It is easy to say that drug interactions should always be considered in any ED presentation, but this approach is not practical. Although many clinical scenarios could theoretically be explained by drug-drug interactions, some of the ones that we should be particularly wary of, especially if patients are on multiple medications, or have recently had a change/addition of a new medication are:
- Delirium/altered LOA
- Any unexplained clinical presentation after initial ED workup