Doctors are being urged to reduce prescribing of antipsychotic drugs to dementia patients after the largest study of its kind found they were linked to more harmful side-effects than previously thought.

The powerful medications are widely prescribed for behavioural and psychological symptoms of dementia such as apathy, depression, aggression, anxiety, irritability, delirium and psychosis. Tens of thousands of dementia patients in England are prescribed them every year.

Safety concerns have previously been raised about the drugs, with warnings to medics based on increased risks for stroke and death, but evidence of other dangers was less conclusive.

New research suggests there are a considerably wider range of harms associated with their use than previously acknowledged in regulatory alerts, underscoring the need for increased caution in the early stages of treatment.

Antipsychotic use in dementia patients was associated with elevated risks of a wide range of serious adverse outcomes, including stroke, blood clots, heart attack, heart failure, fracture, pneumonia and acute kidney injury, the study’s authors reported. Their findings were published in the BMJ.

Charles Marshall, a professor of clinical neurology at Queen Mary University of London, who was not involved with the study, said: “This evidence should prompt renewed efforts to reduce the prescribing of antipsychotics to people living with dementia.

“There are rare circumstances where antipsychotics are genuinely required, and the benefits outweigh these risks, but for the majority of patients with behavioural symptoms that might lead to them being prescribed antipsychotics, we should be focusing on much safer behavioural management approaches.”

The study examined data from 174,000 adults registered at GP surgeries in England who were diagnosed with dementia between 1998 and 2018.

During the study, 35,339 were prescribed antipsychotics – 63% of whom were women – and their medical records were compared with those of dementia patients who were not prescribed these drugs.

Academics from Manchester, Nottingham, Edinburgh and Dundee universities found that dementia patients who were using antipsychotic drugs had a twofold increased risk of developing pneumonia compared with those who were not.

Researchers also found that dementia patients who took antipsychotics had a 61% increased risk of stroke and a 43% elevated risk of breaking a bone. There was also a 28% increased risk of heart attack and 27% increased risk of heart failure.

Patients with dementia who were prescribed antipsychotics appeared to have a 72% increased risk of kidney injury and 62% increased risk of developing a type of blood clot called a venous thromboembolism. The elevated risks appeared to be highest in the first week after treatment.

The study was observational so no firm conclusions could be made about cause and effect. But the authors wrote: “The range of adverse outcomes was wider than previously highlighted in regulatory alerts, with the highest risks soon after initiation of treatment.”

Prof Darren Ashcroft, the study’s senior author, from the University of Manchester, said: “In recent years, it has become clear that more people with dementia are being prescribed antipsychotic drugs, despite existing regulatory safety warnings.

“It is important that any potential benefits of antipsychotic treatment are weighed carefully against the risk of serious harm, and treatment plans need to be regularly reviewed in all health and care settings.”

Commenting on the study, Dr Sheona Scales, the director of research at the charity Alzheimer’s Research UK, said the findings suggested the risks may be more severe than previously understood, which was “particularly concerning given the rise in their use during the pandemic”.

Dr Tom Russ, an honorary consultant psychiatrist at the University of Edinburgh, added: “This study does not suggest to me that these medications should never be used, but they should be used sparingly in situations where other avenues have been explored.”

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