An antipsychotic drug has been found to relieve symptoms suffered by millions of people with Alzheimer's disease worldwide.
A study published in the journal Lancet Neurology found that pimavanserin significantly improves psychosis symptoms in people with the condition, without the devastating side-effects of currently-used antipsychotics.
Researchers also found that the drug had an even greater benefit in those with the most severe psychotic symptoms.
Around half of the 45 million people worldwide who suffer from Alzheimer's disease experience psychotic episodes and there is no approved safe and effective treatment for these distressing symptoms, a figure that is even higher in some other forms of dementia.
In people with dementia, widely-used antipsychotics lead to sedation, falls and can double the speed at which brain function deteriorates.
Their use increases risk of falls, and leads to 1,660 unnecessary strokes and 1,800 unnecessary deaths in the UK every year.
Despite all of these negative effects, they have very little benefit in improving psychosis in people with dementia.
The scientists said that pimavanserin works differently to other antipsychotics, by blocking a very specific nerve receptor in the brain.
Now, it has been found to effectively reduce symptoms of psychosis in people with Alzheimer's disease without the damaging effects of other antipsychotics.
"Psychosis is a particularly terrifying symptom of Alzheimer's disease," said Professor Clive Ballard, from the University of Exeter Medical School.
"People may experience paranoia, or see, hear or smell things that are not there. It's distressing both for those experiencing the delusions and for their carers.
"It's particularly encouraging that most benefit was seen in those with the most severe psychotic symptom, as this group is most likely to be prescribed antipsychotics.
"We are talking about vulnerable elderly, frail people who are suffering terrifying symptoms, being sedated with current antipsychotics even though its well known that they cause terrible health issues and even death in people with dementia, and have very little benefit.
"We urgently need to do better by them, and our encouraging results provides hope. We're delighted that our results have led to a larger phase three clinical trial which is now ongoing."
The findings are the result of a double-blind, placebo-controlled exploratory trial designed to evaluate the efficacy and safety of pimavanserin in 181 patients with Alzheimer's disease psychosis, with 90 of them given pimavanserin and 90 of them on a placebo.
Its safety and efficacy in reducing psychotic symptoms in dementia is now being assessed in a larger-scale clinical trial in the US.
Pimavanserin has been approved for use by the Food and Drug Administration in the US for this purpose, but has not yet been submitted for approval to the European equivalent, the European Medicines Agency.