Reuters reports that an antipsychotic drug frequently given to Alzheimer's patients actually worsens their illness, researchers say. Patients given AstraZeneca's Seroquel had a marked deterioration of memory and other higher brain functions compared to those on placebo, according to Professor Clive Ballard of the Institute of Psychiatry and colleagues. AstraZeneca, Europe's third largest drugmaker, disputed the findings.

Drugs such as Seroquel, which was originally developed to tackle schizophrenia, are increasingly used to treat the personality changes and aggression often associated with Alzheimer's disease.

They are not approved by regulators for dementia but are often prescribed by doctors on an "off-label" basis for patients who develop serious behavioural problems. In one form or another, antipsychotics are used in up to 45 percent of British nursing homes, experts estimate.

"It's a big potential threat to patient health," Ballard told Reuters.

There have been concerns that the two most commonly used antipyschotics, Eli Lilly and Co's Zyprexa and Johnson & Johnson's Risperdal, may increase the risk of stroke -- something British healthcare regulators warned about last year. But, writing in the British Medical Journal, Ballard said Seroquel was not a viable alternative.

His team studied 93 patients with dementia in the northeast of England over six months and found those taking Seroquel experienced a doubling in cognitive decline compared with patients given a dummy pill