A drug used to treat nursing home patients suffering from dementia is making their condition worse, according to research carried out in the region.

Researchers found quetiapine, a common treatment for agitation in people with illnesses like Alzheimer which is also known as Seroquel, affected their higher brain functions making them worse.

Antipsychotic drugs are used in up to 45% of nursing homes to help with agitation, a common and distressing symptom of dementia. The research team was led by Professor Clive Ballard, now of Kings College, London but who began the study while he was head of old age psychiatry at Newcastle University.

They found that when given a placebo as treatment for these symptoms patients showed little change, reported the British Medical Journal.

But those patients given the antipsychotic drug quetiapine showed a deterioration of higher brain functions (cognitive decline).

This is particularly significant as quetiapine had been regarded as one of the safer of the antipsychotic drugs available, said the study authors.

Researchers looked at 93 patients with dementia living in care facilities in Newcastle.

Those in the study taking quetiapine experienced a doubling in cognitive decline compared with the control group who had been given placebo.

Those taking another antipsychotic in the trial, rivastigmine, showed little or no worsening of their illness - but no improvement in symptoms above the placebo group.

The current study highlights concern regarding the safety of quetiapine, and suggests it should not be an alternative to other medications. The authors said in their conclusion: ''Quetiapine and rivastigmine seemed of no benefit in patients with dementia and agitation in institutional care, and quetiapine was associated with greater cognitive decline than the placebo.

''Our results suggest that quetiapine should not be used as an alternative treatment to risperidone or olanzapine in people with dementia and highlight concerns regarding the long term use of antipsychotics in these patients.''

Rebecca Wood, Chief Executive of the Alzheimer's Research Trust, said "These results show the huge and pressing need to develop new and safe treatments for people with dementia. Research into Alzheimer's is severely under-funded and we desperately need to do more to accelerate progress towards finding.

The company which markets Seroquel, AstraZeneca, contests the claims.

A spokesman said the company remains confident of the drug's safety and effectiveness.

According to AstraZeneca more than 8m people have used the drug since 1997.