THURSDAY, Aug. 28 (HealthDay News) -- All antipsychotic drugs can increase the risk of stroke, but the risk is greatest among older patients with dementia, British researchers report.

Concerns about the risk of stroke and antipsychotics were first raised in 2002, especially in people with dementia. In 2004, Britain's Committee on Safety of Medicines recommended that antipsychotics not be used in people with dementia. And, in 2005, the U.S. Food and Drug Administration ordered manufacturers of atypical antipsychotics to add a black box warning to their products about the increased risk for stroke.

"Antipsychotics are effective in treating potentially very distressing psychiatric symptoms, but as with all drugs, their use can be associated with a range of benefits and possible side effects," said study author Dr. Ian Douglas, a research fellow at the London School of Hygiene and Tropical Medicine. "This study has further clarified the potential for antipsychotics to increase the risk of stroke."

Both typical (first generation) and atypical (second generation) antipsychotics are associated with an increased risk of stroke, Douglas said. "This risk is substantially higher in patients with dementia than those without. These findings need to be factored into prescribing decisions made by doctors caring for patients with often-distressing and difficult-to-treat psychiatric symptoms."

For the study, Douglas and his colleague Liam Smeeth, a professor of clinical epidemiology, collected data on 6,790 patients who had suffered a stroke and were taking antipsychotic drugs. Patients taking antipsychotic drugs were 1.7 times more likely to have a stroke, and patients with dementia taking antipsychotics were 3.5 times more likely to have a stroke.

The risk for stroke was slightly higher for people taking the newer atypical antipsychotics, compared with people taking the older typical antipsychotics. Atypical antipsychotics include drugs such as Abilify, Clozaril and Zyprexa. Typical antipsychotics include Thorazine, Haldol and Clopixol.

The study authors did not look at the potential mechanisms associated with antipsychotics that cause stroke, or why the risk appears higher with atypical antipsychotics.

"We believe that the risks associated with antipsychotic use in patients with dementia generally outweigh the potential benefits, and, in this patient group, use of antipsychotic drugs should be avoided wherever possible," Douglas said. "For other patients, careful consideration must be given to the likely individual risks and benefits of any prescribing decision."

The findings were published online Aug. 29 in the British Medical Journal.

Dr. Sam Gandy is associate director of the Alzheimer's Disease Research Center at Mount Sinai Medical Center in New York City, and chairman of the Alzheimer's Association's national medical and scientific advisory council. He said the new study addresses an "important topic and elevates the concern about risks of antipsychotics to a whole new level. The FDA [U.S. Food and Drug Administration] might investigate whether availability limitations or warning labeling should be imposed.

More information

To learn more about antipsychotics, visit the National Institute of Mental Health.