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One in 10 hospitalisations for older people are linked to adverse drug reactions, study says

Blood-thinning medications such as warfarin and aspirin accounted for one-third of ADR-related admissions in the RCSI study

Tiberius Pereira (58), a senior executive in the tech industry, was diagnosed with chronic kidney disease eight years ago and was put on a number of medications to help lessen his symptoms.

“I was in a fast-paced working environment and travelled a lot for work. I was quite bewildered when I became ill as I was reasonably healthy, took regular exercise and had a good diet,” Pereira told The Irish Times.

Within a few months, he developed a rash all over the trunk of his body. “I told the nephrologist who was treating me. He became seriously concerned and admitted me to the high dependency unit at Beaumont Hospital,” explained Pereira.

His doctor decided to stop all his medication and to reintroduce drugs to treat his blood pressure and other symptoms one by one to isolate which was causing his rash. “Once I was put back on Plaquenil [hydroxychloroquine] which was being used to treat symptoms of lupus, the rash returned. I was told I had drug hypersensitivity syndrome which causes severe unexpected reaction to a medicine and affects several organ systems at the same time. This meant I definitely needed a kidney transplant and within a year of my first symptoms, I received a donor kidney from my sister.”


Following his recovery from transplant surgery, Pereira got his energy back and is exercising again. Reflecting on his experience, he said, “Healthcare is a risky business. Adverse events will happen despite the best efforts of physicians. I had read the all the information about the medications I was on and even though I had a visceral reaction [my body was telling me not to take it] to that particular medication, I continued taking it. My doctor later discovered and told me what the problem was – he didn’t try to cover anything up – and I couldn’t have asked for better care.”

Medication harm or adverse drug reactions (ADRs) are much more common than might be expected. One new study by researchers at the Royal College of Surgeons of Ireland (RCSI) has found that an ADR was the primary reason why one in 10 older patients was admitted to hospital and that an ADR was a contributing factor in why over 40 per cent of these patients ended up in hospital. Blood-thinning medications such as warfarin and aspirin accounted for one-third of ADR-related admissions in the RCSI study. A range of cardiovascular drugs accounted for another one-third of ADR-related admissions.

Shockingly, the study – which will be presented at a Medication Without Harm seminar at the RCSI on Monday – found that 70 per cent of all ADR-related admissions were “deemed definitely or possibly preventable or avoidable”.

Professor David Williams, professor of stroke medicine at RCSI, consultant in stroke medicine at Beaumont Hospital and co-author of the study said that an ageing population has multiple conditions requiring different medications which can lead to adverse drug reactions.

“It can be very unpredictable with older patients on multiple medications. Doctors have to weigh up the risks and benefits for each patient and accept a certain risk in the hope that the patient will benefit,” said Prof Williams.

In some instances, the addition of a short-term medicine (eg certain antibiotics) to treat an infection can inhibit or prevent the absorption of another drug used to treat a chronic condition, leading to a toxic reaction. Not knowing exactly which medications some patients are taking adds a further complication to discovering if a patient has had an adverse drug reaction.

“It can be a minefield finding out exactly what medications patients are on. People can take medications that doctors aren’t aware of and some take other people’s medicines. Vulnerable individuals may also forget if they have taken their medicine or not,” he added.

Another recent study of older patients in 15 GP practices in Ireland found that one in four older people had at least one ADR over a six-year period. “Nine out of ten of these adverse drug reactions were mild [eg nausea] but patients prescribed 10 or more medicines were over three times more likely to experience an ADR,” said Professor Emma Wallace, professor of general practice at University College Cork (UCC) and co-author of the study.

This study found that medicines prescribed for cardiovascular problems, nervous system and infections (ie antibiotics) were those most associated with an ADR. And one-third of the patients who had a moderate adverse drug reaction (10 per cent of all patients with an ADR) required emergency hospital admission.

Polypharmacy which is defined as taking more than five prescribed medications regularly – and is more common in older people – is the primary risk factor for ADRs. Experts agree that adverse drug reactions can be difficult to identify in older people with multiple conditions because the symptoms are non-specific (eg delirium, drowsiness, falls, fatigue and constipation).

Adverse drug reactions can also be mistaken as the onset of a new medical problem rather than being caused by a particular medicine. This can sometimes lead to the addition of a new medicine – known as the prescribing cascade – causing potential additional risk to the patient.

Patients most at risk of ADRs are those on multiple and/or higher-risk medications and those going into or coming out of hospital.

The authors of the aforementioned study of older patients attending GPs in Ireland recommend structured medication reviews in general practice to address the estimated 10 per cent of over-prescribing of medications in primary care. They also concluded that their study showed that addressing polypharmacy is a critical issue in reducing the burden of medication and lessening the likelihood of ADRs for vulnerable patients.

Approximately half of ADR could be prevented when pharmacists work with patients in GP practices to carry out these reviews

—  Prof Ciara Kirke

“As we age, we are more likely to live with several long-term health conditions that require multiple medications. Balancing the benefits of each medicine against the potential risks can be challenging. It’s a good idea for older people taking 10 or more long-term medicines to have a regular medication review with their doctor or pharmacist,” said Prof Wallace.

Ciara Kirke, pharmacist and HSE clinical lead for the National Medication Safety Programme, said that while many GPs are keen to have pharmacists work in family practice to do comprehensive medicine reviews for patients with complex medicine needs, the costs of employing them is prohibitive. Citing a recent collaborative project with GPs in Northern Ireland and Scotland, Kirke said that 63 per cent of patients reported fewer side effects following comprehensive medicines reviews with pharmacists in GP practices. The number of medicines patients were on was significantly reduced in some cases.

“Approximately half of ADR could be prevented when pharmacists work with patients in GP practices to carry out these reviews,” said Kirke. The HSE is currently looking into how such a service could be funded.

A small number of GP practices in Ireland employ a pharmacist part-time to carry out medicine reviews. Residents of nursing homes must have medicines reviews every three months, under the Health Information and Quality Authority rules for nursing homes. Patient advocacy groups and health professionals encourage people to know their medicines and keep an up-to-date list of their medicines with them at all times.

Sylvia Thompson

Sylvia Thompson

Sylvia Thompson, a contributor to The Irish Times, writes about health, heritage and the environment