Antidepressant drug citalopram could help significantly relieve agitation in patients with Alzheimer's disease, but at the cost of slightly decreasing cognitive function and increasing heart attack risk, according to results of a clinical trial released Tuesday.

However, the drug, sold under the brand names Celexa and Cipramil and also available as a generic medication, might be safer than antipsychotic drugs currently used to treat the condition, according to the study led by Johns Hopkins Medicine researchers that included seven other academic medical centers in the United States and Canada.

Antipsychotics are often used as first-line medications for Alzheimer's-related agitation, but the researchers said they significantly increase the risk of strokes, heart attacks and deaths.

The researchers recruited 186 patients with Alzheimer's disease who showed a collection of symptoms including emotional distress, excessive movement, aggression, disruptive irritability and disinhibition.

In the nine-week study, the patients were separated into two groups. About half took increasing doses of citalopram that peaked at 30 milligrams per day, and the rest took an identical-looking placebo.

The study results showed that about 40 percent of the patients who took citalopram had "considerable relief" in terms of agitation compared to 26 percent of the patients who took the placebo.

However, patients on the drug were also more likely to have slightly decreased cognitive function.

"It was not huge, but measureable," said lead author Constantine Lyketsos, director of the Johns Hopkins Memory and Alzheimer's Treatment Center and director of the Department of Psychiatry at Johns Hopkins Bayview Medical Center. "That introduces a tradeoff."

Patients on citalopram also had longer QTc intervals, a measure of abnormal heart function that increases the risk of heart attacks. But Lyketsos said antipsychotic medications increase heart attack risk as well, perhaps even more substantially.

The researchers next planned to test if a lower dose of citalopram might be just as effective in treating Alzheimer's- related agitation but with less risk for cognition and heart function.

The findings were published in the Journal of the American Medical Association.