Interview #7: Prescribing cascades and the implications for deprescribing

Hello, deprescribers! We are back again after a quiet few months with some more blog content. Today we are talking about prescribing cascades with Dr. Sameera Toenjes from University of Toronto (Canada). We hope that after this interview you will have “can this symptom be caused by a drug?” imprinted on your brain (though most of you probably already do!).

Dr. Toenjes is a pharmacist currently pursuing a Master of Science in Pharmaceutical Sciences under the supervision of Dr. Lisa McCarthy. She enhances patient care through her part-time work with the Bruyère Deprescribing Research Team ( and clinical practice at Women’s College Hospital.

For her master’s thesis, Dr. Toenjes is applying qualitative research methods to better understand how to address prescribing cascades, an important and under-recognized contributor to polypharmacy.

Q: We suspect most of our audience will know the answer to this one but just in case – can you tell us what a prescribing cascade is?

Dr. Toenjes: I think this is a great and an important question because many people can likely think of a prescribing cascade they’ve seen in their own lives when they hear the definition, but often have not heard the phrase “prescribing cascade”. I think that really speaks to the invisibility of the problem.

A prescribing cascade happens when someone takes a medication, experiences a side effect and that side effects gets treated with another medication. In practice, this often happens when prescribers attribute patients’ new signs or symptoms to a medical condition rather than a medication side effect.

Q: And, more importantly, why is it important to study prescribing cascades?

Dr. Toenjes: We care about prescribing cascades because they are common and under-recognized contributors to polypharmacy.

Let’s take the example of the calcium channel blocker (CCB) – edema – diuretic cascade. A study using health claims data in Ontario, Canada showed that adults aged 65 years and older starting a CCB had a higher rate of being prescribed a loop diuretic within 90 days – about a 1.4% rate increase. Although that rate may sound low, on a population level the numbers are high. We know from prescription record data that about 21% of older adults in Canada are prescribed a CCB. This means for the 1.5 million older adults who receive a CCB in Ontario, 20,820 (or 1.4%) may receive a new and potentially unnecessary diuretic prescription.

There is also some preliminary evidence that prescribing cascades negatively impact quality of life. For example, a study using Medicare data found that experiencing a cascade (CCB – edema – diuretic) is associated with a statistically and clinically significant decline in physical functioning.

Q: Can you tell us a little bit about the work you have been doing related to prescribing cascades and give our audience some key takeaways?

Dr. Toenjes: Yes, I’m really excited about it! I’m still in the planning stages for my Master’s thesis but I’m excited to join this team that includes Drs. Lisa McCarthy, Barbara Farrell, Lianne Jeffs, Colleen Metge and Sara Guilcher. For about the past 4 years, our research team has been working on understanding how and why prescribing cascades occur in practice and opportunities for interventions (both at the patient and healthcare system levels).

There are some key takeaways from their work that I find really interesting. First, there is variability in terms of awareness about medication side effects and the phenomenon of prescribing cascades – health care professionals and the public alike may not connect the pieces. And second, even when people identify the problem of a potential prescribing cascade, they struggle to know what to do, particularly when they are not the original prescribers or don’t have all the information and tools they need to investigate it.

Now we’re at the step of developing an intervention to help with those two issues. My thesis involves leading focus groups to better understand what clinicians need in an intervention and how to bring that intervention to practice. I’ve taken courses for my Master’s on qualitative research and implementation science, and I’m really excited to apply the principles I’ve learned!

Q: How often do you come across prescribing cascades in your clinical practice, and how you do you approach addressing them?

Dr. Toenjes: All the time! That’s one of the main reasons I got really excited about this topic for my research! They are everywhere once you start looking for them! It feels like connecting puzzle pieces when you start to notice them.

I remember the first patient I cared for on rotation with a primary care team. She was referred because she was very concerned about metoclopramide’s risk of tardive dyskinesia after reading about it on the internet. At first, I looked into the evidence and thought to reply back about the very low risk of tardive dyskinesia and how she can be attentive about the early signs. But my preceptor, who was great at catching cascades, asked me to re-assess if metoclopramide was indicated in the first place. When I looked at her medication history, turns out it was a prescribing cascade!

She had a number of anticholinergic medications on her list that were causing gastroparesis. And she was using metoclopramide to alleviate the bloating and stomach discomfort. We were able to deprescribe some of those anticholinergics, improve her gastroparesis, and avoid the risk of tardive dyskinesia altogether! It was awesome!

Since then, I’ve made an active effort to think through each presenting sign and symptom or listed medical condition to ask – “could this be caused by a drug?” Often this question can be difficult to answer, but in my experience, primary care clinicians can be incredibly effective at tackling this problem and improving their patients’ quality of life!

Q: And finally, one question we ask all our interviewees – what is your most satisfying deprescribing target and why?

Dr. Toenjes: Fun question for a pharmacist like me to nerd out on!

Hmmm, it’s a tough question though because I love shortening medication lists. Who doesn’t? If I had to choose, I would say anticholinergics may be my most satisfying deprescribing target. In the past, it’s been particularly satisfying to stop these medications with women who are having issues with urinary incontinence. I have heard so many stories from women struggling to plan their lives around needing to access a washroom every hour. It’s exhausting and the impact of people being afraid to leave their homes for long stretches often leads to isolation.  We’ve all had a taste of staying closer to home with COVID-19 and the impact of isolation – imagine that resulting from a medication side effect that we can do something about!

Thank you to Dr. Toenjes for taking the time to chat about prescribing cascades. We look forward to seeing the work she is doing on developing an intervention to address prescribing cascades in practice.

You can find Dr. Toenjes on Twitter: @sameera_toenjes

More reading on prescribing cascades

Photo by Towfiqu barbhuiya on Unsplash