Drug Interactions
Sonya Collins
About a third of American adults in their 60s and 70s take five or more prescription drugs regularly. Often, some of these drugs are the result of prescribing cascades, which can be unnecessary and may cause avoidable adverse effects and adverse events.
Prescribing cascades, which are when a patient has an adverse event that a prescriber misinterprets as a new health condition and prescribes another drug for it, are relatively common among older adults, but little is known about the potential risks associated with prescribing cascades.
One type of cascade—a prescription for a calcium channel blocker followed by a diuretic—may significantly raise the risk for serious adverse events, according to a recent study in the February 2024 issue of the Journal of the American Geriatrics Society.
“Not all prescribing cascades are potentially inappropriate, but prescribers at least need to think about the possibility and decide accordingly,” said Paula Rochon, MD, a coauthor of the study and a professor at the University of Toronto.
Prescribing cascade led to adverse events
In the study, researchers reviewed health administrative data on 39,347 community-dwelling older adults with hypertension and no history of heart failure who were newly dispensed a calcium channel blocker. Among them, 1,881 experienced a prescribing cascade and were prescribed a diuretic within 90 days of the calcium channel blocker.
Compared to those who did not get a subsequent prescription for a diuretic, those in the cascade group were 21% more likely to have a serious adverse event, indicated by an emergency department visit or hospital admission within the first 90 days of follow-up. The cascade group continued to have higher rates of serious adverse events up to 180 days during follow-up.
Don’t rule out drug adverse effects
The study findings do not necessarily suggest that diuretics should be contraindicated for people who are taking calcium channel blockers, Rochon stressed. The study should, rather, serve as a reminder for prescribers and pharmacists to consider the possibility of a prescribing cascade and evaluate whether the second drug is appropriate.
“We have to ask whether the existing drug therapy could be causing the new medical condition, which, in this case, was edema,” Rochon said.
If so, clinicians should consider whether they can lower the dose of the primary drug and whether the primary drug is needed at all.
“This should make you go back and think about what started this whole prescribing process in the first place,” she added.
Research has identified numerous possible routes for prescribing cascades. A 2023 systematic review in Frontiers of Pharmacology found calcium channel blockers to be the most common lead drug in a prescribing cascade, initiating 13 possible cascade routes. The other most common initial drugs in a cascade were antipsychotics, gastroprokinetics, acetylcholinesterase inhibitors, and antibiotics. Polypharmacy was also a leading cause of a prescribing cascade.
Record-keeping
Community pharmacists may take the study findings as a reminder to encourage patients to keep a detailed list of their current medications, including when the medication was started and, importantly, why it was started.
“When these medications are used over long periods of time, that information often gets lost,” Rochon said. “So it’s helpful to encourage patients to keep a record of those things.” ■