Doctors should consider all antipsychotic medications to be equally risky for seniors, say researchers, who suggested additional warnings for the drugs are warranted.

In 2005, both Health Canada and the U.S. Food and Drug Administration warned that newer antipsychotic drugs increased the risk of death among elderly patients with dementia.

The newer antipsychotics such as Zyprexa (olanzapine), Seroquel (quetiapine) and Risperdal (risperidone) were developed for schizophrenia, but doctors may prescribe them for dementia.There is no strong evidence that the drugsare effective for Alzheimer's.

The warnings left the impression that older, conventional antipsychotics were safer.

To test the idea, Dr. Sebastian Schneeweiss of Harvard Medical School in Boston and his colleagues reviewed death rates among more than 37,000 people aged 65 and older in British Columbia who took antipsychotic drugs between January 1996 and December 2004.

Some people in the study took older antipsychotic such as haloperidol and chlorpromazine while others took the newer, atypical variety.

Patients prescribed the conventional antipsychotics showed a 32 per cent greater risk of death within 180 days compared with those given an atypical antipsychotic, the team reports in Tuesday's issue of the Canadian Medical Association Journal.

Expand warning

The increased risk of death was larger than that from all other health conditions measured in the study except congestive heart failure and HIV infection, the researchers said.

"Together with earlier findings, the results from our study strongly suggest that Health Canada and the FDA should include conventional antipsychotic medications in their public health advisories, which currently warn only of the increased risk of death associated with the use of atypical antipsychotic medications in elderly patients with dementia," the study's authors concluded.

It is possible that doctors prescribed the older antipsychotic haloperidol more often than newer medications in patients who were more likely to die, or that patients using the antipsychotic drugs were more impaired physically and cognitively, the researchers acknowledged.

Scientists do not know why conventional antipsychoticmedications seem to increase short-term mortality.

4 additional deaths

Using patient data from British Columbia, the authors compared 12,882 people over age 65 taking the older drugs to 24,359 seniors taking the atypical drugs.

Within the first six months of treatment, 14.1 per cent of the people on the conventional drugs died, compared to 9.6 per cent in the atypical antipsychotics group.

"In these analyses, the adjusted risk difference … meant that, for every 100 patients prescribed a conventional antipsychotic drug instead of an atypical drug, there were about four additional deaths," they wrote.

Reasons for the increased risk of death aren't clear, they note, though some evidence points to increased risk of heart-related conditions, impact on blood pressure and swallowing problems as potential explanations.