An antidepressant appears to work as well as the most commonly prescribed antipsychotic drug in treating agitation and aggressive behaviour in people with Alzheimer's — minus the severe side-effects, a Canadian study suggests.

Researchers at Toronto's Baycrest geriatric centre and the Centre for Addiction and Mental Health teamed up to conduct a head-to-head trial of the antidepressant citalopram (Celexa) and the antipsychotic risperidone (Risperdal) in non-depressed patients with dementia.

During the 12-week study, 53 patients were treated with citalopram, a selective serotonin re-uptake inhibitor or SSRI, and 50 received risperidone. Researchers found that the two medications were almost equally effective in controlling psychotic behaviour in patients.

Yet citalopram did not cause the often-severe adverse effects of risperidone, which can include unwanted sedation, increased confusion and the development of Parkinson's-like symptoms.

"But the thing that was the biggest surprise to us was that we didn't hypothesize this," said principal researcher Dr. Bruce Pollock, a geriatric psychiatrist at Baycrest.

"We thought that citalopram would be better for agitation — impulsivity and aggression — which we know SSRIs help with, but the so-called psychotic symptoms were treated as well with the antidepressant as they were with the antipsychotic."

The study is published online Monday by the American Journal of Geriatric Psychiatry.

Psychosis a common outcome

Pollock said about 90 per cent of people with Alzheimer's will develop psychosis at some point in their illness.

"The most disturbing part for families and caregivers are the psychotic symptoms, and often these take the form of what we call paranoid delusions or often visual hallucinations, although they could be auditory as well."

In the grip of these psychotic episodes, patients can become extremely agitated, aggressive and sometimes even violent, he said.

Terry McAndrew of Thornhill, Ont., north of Toronto, said her father has been treated with antipsychotic medication for more than a decade for agitation and paranoid delusions, and suffered severe side-effects as a result. She has fought hard over the years to have his doctor limit the dose of the drug, which would leave him "just zoned out" and caused him to develop Parkinson's-like symptoms such as tremors and a shuffling gait.

"If they would have had this 10 years ago, it would have been great," McAndrew said of the effectiveness of citalopram.

Pollock said that the neurochemical causes of delusions and hallucinations in schizophrenia and Alzheimer's are radically different, and can lead to side-effects in one patient group that don't show up in the other.

Antipsychotics increase risk of death in elderly

In fact, in 2005, both Health Canada and the U.S. Federal Drug Administration ordered manufacturers of risperidone and other "atypical antipsychotics" to put a "black box" warning on their products after they were found to increase the risk of early death in elderly patients.

Dr. Sudeep Gill, a geriatrician at Queen's University, led a study published earlier this year on risperidone and similar antipsychotics. The researchers found that the drugs increased the risk of death in dementia patients within 30 days of starting them, an effect that persisted for six months.

Gill called the citalopram-risperidone comparison trial, which he was not involved in, an interesting and important study that may provide physicians with a new direction for treating psychosis in patients with dementia.

But he agreed with the authors that more research is needed.