Women and patients taking more drugs are more likely to experience side effects, a new study of older adults suggests.
A quarter have experienced at least one adverse drug reaction (ADR) over the six-year period studied by Cork researchers.
The researchers found that patients who were prescribed 10 or more medications had three times the risk of developing a reaction.
This is believed to be the first general practice study to address this issue and has been followed up in older patients for several years.
As a result of their findings, the researchers recommended that older people taking 10 or more medications should be prioritized for regular reviews, and GPs should consider stopping prescribing ineffective medications.
The study, published in the British Journal Of General Practice, monitored 592 patients aged 70 and over from 15 general practices in the Republic of Ireland over a six-year period.
Overall, most of the side effects identified were mild and resolved, the researchers said.
About 11% were of moderate severity, while eight patients had to be admitted to hospital as a result of their reactions.
Women were at least 50% more likely to have ADRs than men, which the study authors said was similar to previous studies.
Co-author Professor Emma Wallace from University College Cork said the difference in risk between the sexes could be due to a number of factors.
She said: “Women and men can react differently to the effects of drugs, both beneficial and harmful, and the way our bodies process and break down drugs can vary by gender. The type of medication prescribed may also differ between men and women.”
The drug groups most commonly associated with side effects in this study included those used to treat high blood pressure and other heart conditions, strong painkillers such as tramadol, and antibiotics such as amoxicillin.
Examples of side effects included dry mouth, swollen ankles, headaches and nausea.
The article stated: “Adverse effects can be difficult to identify in the elderly with a medically complex presentation because they often present as non-specific symptoms.
“GPs are well placed to detect adverse reactions to medications prescribed in primary care as well as in other care settings.
“Stop prescribing drugs that are ineffective and those that are no longer clinically indicated is one way to reduce the risk of side effects in older patients.”
Professor Wallace said: “I was very interested in looking at this from a GP’s perspective in terms of how common the problem is and how serious adverse drug reactions are.
“We found that one in four older people experienced at least one adverse drug reaction over a six-year period. Most adverse drug reactions were clinically mild, but 11% were moderate in severity, and eight patients were hospitalized urgently as a result of an adverse drug reaction.
“We found that women and people who were prescribed more and more medications were more likely to experience adverse drug reactions. Specifically, patients who were prescribed 10 or more medications had a threefold greater risk of side effects.”
Asked about the significance of the study, Professor Wallace said: “As we get older, we are more likely to live with several long-term conditions that require multiple medications.
“This study shows that while just over a quarter of older adults had at least one side effect of the drug, most of these side effects were mild and resolved.
“It’s a good idea in particular for older people who are taking 10 or more long-term medications to have regular medication reviews with their doctor or pharmacist.”
The study was funded by the Health Research Board of Ireland.