Drug side effects can trigger a ‘prescription cascade’

As we all know, modern drugs are very effective and reliably relieve the various medical conditions for which they are prescribed – heartburn, hypertension, insomnia and so on. This is all for the better. But care must be taken to ensure that the symptoms treated with one drug are not just the adverse effects of another.

This is the phenomenon of the “cascade of prescribing” first identified more than 25 years ago, when it was noted that a disproportionate number of those who started taking antihypertensive pills were taking anti-inflammatory arthritic drugs (such as ibuprofen). From this it could be deduced that these were not two independent disorders, but that the anti-inflammatories were responsible for the increased blood pressure.

Since then, dozens of such “cascades” have been identified – some quite long. For example, amlodipine, often prescribed for hypertension, can cause ankle swelling. This leads to the prescription of a diuretic (water pill) that, among the other side effects, makes you more susceptible to diabetes, requiring even more drugs to lower blood sugar – and so on.

The permutations are virtually unlimited. Geriatrician Denis O’Mahoney recently reported that four patients with a variety of conditions – allergic rhinitis, hallucinations, slow heart rate and incontinence – were all taking the same drug, donepezil, for early dementia. In all cases, their symptoms had been misinterpreted as a new disease and unnecessary treatment was initiated, while stopping donepezil would have been the appropriate course of action.

There can be no one-size-fits-all solution to such a ubiquitous phenomenon than to be constantly alert to the possibility of a cascade as a likely culprit when examining a patient.

A more benign angina

Transient gripping pains radiating to both arms (similar to “the pressure” one experiences when taking blood pressure), as reported recently in this column, are suggestive, notes primary care physician Robert Walker, of Prinzmetal’s angina. This differs from the usual form (which is caused by heart disease) in that it occurs spontaneously at rest rather than being triggered by exercise. In either case, the blood supply to the heart muscle is insufficient for its needs; but in Prinzmetal it is due to spasm of the coronary arteries rather than (as in heart disease) that they are narrowed by atheroma. The cause is elusive, but since the heart’s functioning is otherwise normal, the prognosis is benign.

Rest after dinner

This week’s question comes courtesy of Ms SA from Southampton, who writes on behalf of a close friend in his early fifties: “extremely energetic with a wiry physique”. This friend avoids eating during the day, but invariably gets very sleepy soon after dinner, to the extent that she is only vaguely aware of what is going on around her. This lasts up to three hours, during which she can only be awakened with difficulty before returning to her semi-comatose state.

This postprandial drowsiness can follow any meal (hence she doesn’t eat until evening), with dairy and sweet foods being the most obvious trigger. “She would of course like to have ideas about the possible cause and treatment of this condition,” she writes.

Magnet therapy

Finally, several readers have written to me about their pleasant surprise – despite considerable skepticism – about the apparent efficacy of magnetic devices. “I thought it was a bad joke,” one gentleman recalls, when an acquaintance suggested buying a magnetic bracelet for his aching knee — only to be “amazed at the almost instant relief.”

Also surprised were researchers at the Peninsula School of Medicine at Exeter University when a study designed to demonstrate the questionable credentials of magnetotherapy came to the opposite conclusion. In evaluating outcome in 200 patients with arthritis of the hips or knees, Dr. Tim Harlow and colleagues provided “a clinically useful advantage” in those who wore a magnetic bracelet compared to a steel ring bracelet. It is admittedly difficult to explain how a localized magnetic field generated at the wrist should relieve painful symptoms in a distant part of the body (the hips and knees); but there’s a lot in medicine that we don’t really understand.

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