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Prescription rates of certain antipsychotic drugs given to seniors with dementia have increased significantly despite safety warnings in recent years, according to a new study that questions the effectiveness of the warning mechanisms used by drug makers and Health Canada.

The findings, published today in the Canadian Medical Association Journal, reveal that overall prescriptions of atypical antipsychotic drugs to elderly people suffering from dementia - many of whom live in nursing homes - jumped 20 per cent between 2002 and 2007. Three major safety warnings were issued during that period. "The point is the warnings had a limited impact," said Geoffrey Anderson, professor in the department of health policy, management and evaluation at the University of Toronto and an author of the study. "These are human beings ... It's our duty to protect the care for them."

Atypical antipsychotic drugs are a relatively new class of "second generation" antipsychotic drugs used to treat schizophrenia and other serious psychological problems.

Health Canada issued the first warning about the atypical antipsychotic drug risperidone, sold under the brand name Risperdal, in 2002 after studies showed it was associated with an increased risk of stroke in older dementia patients. Another warning was issued in 2004 about the atypical antipsychotic olanzapine, sold under the name Zyprexa, amid fears of increased risk of stroke and other health issues.

A third blanket warning about the potential risks followed in 2005 after numerous studies showed the drugs were associated with an increased risk of death.

Despite these warnings, the number of prescriptions for atypical antipsychotic drugs for seniors increased, according to the study, which suggests the drug makers and Health Canada may have to do more to protect at-risk patients.

"I think one of the things that was brought out in these papers is that maybe these warnings aren't enough," said Paula Rochon, scientist at Toronto's Baycrest Centre and the Institute for Clinical Evaluative Sciences.

"Maybe the warnings need to be complemented with other things, like guidelines."

The findings demonstrate the importance of non-pharmaceutical treatments for dementia patients, and should prompt health-care providers and families to look for alternatives, Dr. Rochon said.

Instead of turning to drugs, it may be beneficial to determine what factors trigger a dementia patient to become agitated, such as the desire to go for a walk or to have a meal, in order to help them, she said.

The drug safety warnings did affect the growth of prescription rates of atypical antipsychotic drugs, but not by much, Dr. Rochon said. Although the rates at which the drugs were prescribed continued to climb in the wake of safety warnings, growth in use was between 3 and 5 per cent lower than expected.

"The rates that those drugs looked like they were increasing was a little bit blunted," she said. "[The warnings] didn't have, I would think, the effect that people might have wanted to have seen on the way the drugs are being prescribed."

Two of the three atypical antipsychotic drugs that have been subject to Health Canada warnings are not even approved for use in elderly patients, raising questions about whether they should be funded under provincial health plans, Dr. Anderson said.

Although Risperdal is approved for use in elderly people with dementia, Seroquel and Zyprexa are not.

Doctors can still prescribe drugs to patients even if the medication is not approved in a particular age group to treat a particular condition - a practice known as "off label" prescribing.

"Why [do provincial health plans] fund the use of these drugs in this population despite three warnings?" Dr. Anderson asked. "It's a particularly vulnerable population. It's not a population in a position to speak for themselves."