Your new symptom might be your old medicine: the 24 chains researchers found

What happened

On 10 September 2026, The BMJ published a study that looked at a problem doctors and pharmacists have a name for: the prescribing cascade. A prescribing cascade happens when a medicine causes a side effect, the side effect is mistaken for a brand new health problem, and a second medicine is prescribed to treat it. The first medicine is never questioned. The patient simply ends up on two. Researchers led by Dr Paula Rochon at the Lunenfeld-Tanenbaum Research Institute, part of Sinai Health in Toronto, went looking for how often this happens in the real world. They used Ontario's prescription records, held by the health data institute ICES, covering nearly 2.3 million adults aged 66 and over who were living in their own homes. They identified 24 common medicine pairings that look like prescribing cascades. Three stood out for how often they occurred within a single year. Iron supplements followed by laxatives came top, happening in 11.9% of cases. Statins followed by painkillers came next, at 10.9%. Medicines for dementia known as cholinesterase inhibitors, followed by something to help with sleep, came third at 10.3%. Dr Rochon summed up the problem plainly: "These sequences of events are common but often missed in clinical practice."

Why this matters

Most people reading this will know someone who takes several medicines every day. It is very ordinary. It is also where small mistakes can quietly add up. Every extra medicine brings its own possible side effects. So if a second medicine is added to fix a problem the first one caused, the door is open for a third. Researchers call this a cascade because, once it starts, it can keep going. The study points out that older adults are more at risk, simply because they tend to take more medicines. It also notes that women are more affected. Women tend to live with more long-term conditions than men, are prescribed more medicines over their lifetime, and have more side effects from them. None of this means the medicines are wrong. Iron tablets treat anaemia. Statins lower the risk of heart attacks and strokes. Cholinesterase inhibitors can help people with dementia. These are useful medicines that help millions of people. The point is narrower, and more useful. When a new symptom appears, one of the first questions worth asking is whether a medicine could be behind it.

What the evidence actually says

It is worth being careful about what this study can and cannot tell us. The researchers looked at prescription records. Records show what was prescribed and when. They do not show what the doctor was thinking, or what the patient described in the room. So the study identifies patterns that look like prescribing cascades, rather than proving that each individual case was one. Some of these pairings will be entirely appropriate. A person taking iron tablets might have had constipation anyway. Someone on a statin might have hurt their knee gardening. What the size of the study does give us is confidence in the pattern. Nearly 2.3 million people is a very large group, and the same pairings turn up again and again. The researchers also give a clear worked example. Anti-inflammatory painkillers, the group known as NSAIDs, can push blood pressure up. If a clinician sees the raised blood pressure and treats it as high blood pressure, the patient goes home on a blood pressure medicine, while the painkiller that caused the rise carries on. The study is from Ontario, Canada, not the UK. Prescribing habits differ between countries. But the medicines involved are common here too, and the underlying idea is not country-specific. The researchers' suggested fixes are practical rather than dramatic: proper medication reviews that look at when each medicine was started and why, more involvement from pharmacists, and computer systems that flag likely cascades to prescribers.

Qurexa perspective

This is a subject close to what we do every day. Qurexa delivers prescriptions and supports people with taking their medicines as intended, so we see how quickly a repeat list can grow without anyone meaning it to. A pharmacist is often the person best placed to spot a cascade, because they can see the whole list in one place. In England, the NHS offers structured medication reviews through GP practices, and community pharmacists run the New Medicine Service for people starting certain treatments. Both are free, and both exist precisely for this kind of question. One small thing that helps more than people expect: keep a single, up-to-date list of everything you take, including anything you buy over the counter and any supplements. Bring it with you. It makes a review far more useful. If we deliver your medicines and you notice your list has grown, it is always reasonable to ask your pharmacist for a proper look at it.

Practical advice

None of this is a reason to stop taking anything. Stopping a medicine on your own can be genuinely dangerous. But there are sensible things you can do. When a new symptom starts, note roughly when it began. Then check whether any medicine was started or changed in the few weeks before. Timing is the single most useful clue, and it is the thing a clinician is most likely to be missing. Ask the direct question. "Could this be a side effect of something I am already taking?" is a fair and normal thing to say, and most prescribers will welcome it. Ask for a medication review if you take several medicines, especially if you are over 65. You are entitled to one, and you do not need a special reason. Keep one list, not several. Include the dose and roughly when you started each one. Include the things that do not feel like medicines. Iron tablets, painkillers bought from a supermarket, herbal remedies and vitamins all count. In the UK you can also report a suspected side effect yourself through the MHRA's Yellow Card scheme. Reports from patients are used alongside reports from clinicians. And if something feels wrong, say so early rather than waiting for the next routine appointment.

What to know

A BMJ study of nearly 2.3 million older adults in Ontario has identified 24 common chains where one medicine's side effect appears to be treated as a new illness with a second medicine. The most frequent were iron tablets followed by laxatives, statins followed by painkillers, and dementia medicines followed by sleep medicines. The study shows patterns rather than proving each case. But it is large, consistent, and points at a fix that is already available to most people: a proper medication review, with a pharmacist involved, that asks when each medicine was started and why. The practical takeaway is a single question worth carrying with you: could this new symptom be coming from something I already take? Sources: The BMJ, study on prescribing cascades in older adults, 10 September 2026, https://doi.org/10.1136/bmj-2026-100499; ScienceDaily (Lunenfeld-Tanenbaum Research Institute), 'Your next prescription could be treating a side effect from the last one', 11 September 2026, https://www.sciencedaily.com/releases/2026/09/260911003843.htm; Medscape, 'Inappropriate Prescribing Cascades Put Older Adults at Risk', September 2026, https://www.medscape.com/viewarticle/inappropriate-prescribing-cascades-put-older-adults-risk-2026a1000xwp This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional. Never stop or change a prescribed medicine without speaking to a clinician first.