NEW YORK(Reuters Health) - Young, physically healthy people who take antipsychotic drugs face an increased risk for potentially fatal blood clots, researchers report.

While the link has been suggested before for certain psychiatric drugs, this study extends earlier findings to a wider range of medications for schizophrenia, manic-depressive disorder, dementia, autism, and other brain disorders.

Looking at nearly 30,000 patients on antipsychotic drugs, researchers found that these patients were seven times more likely than drug-free study participants to develop blood clots known as venous thromboembolisms. The risk was greatest during patients' first 3 months on the drugs.

These findings are not particularly surprising, according to lead researcher Dr. Gwen L. Zornberg of Boston University School of Medicine in Lexington, Massachusetts. For example, the schizophrenia drug clozapine has already been tied to venous thromboembolism. Moreover, Zornberg said in an interview with Reuters Health, doctors have been noting for decades that antipsychotic drugs seem to trigger blood clots in some patients.

"What's fascinating," she said, "is that this was very well-studied from the 1960s until 1984...then for some reason it just fell through the cracks."

Research on the link between the drugs and blood clots has been hindered by the fact that study patients have often had other risk factors for venous thromboembolism. To avoid this problem, Zornberg's team focused on patients younger than 60 who had no risk factors for blood clots, such as heart disease or diabetes.

Over an average of 7 years, 42 patients on antipsychotic drugs developed a venous thromboembolism--a risk seven-times greater than among people not taking the drugs.

Why the risk was highest early on is unclear, according to Zornberg. She speculated that some people may be particularly vulnerable to blood clots and develop them quickly.

"The major thing is for both doctors and patients to be aware of the possibility for blood clots," Zornberg said, noting that they may be prevented by something as simple as exercise. Bedridden patients, she added, should receive physical therapy to boost their activity.

Many doctors may not know to consider blood clots when psychiatric patients have telltale symptoms such as leg pain or difficulty breathing, Zornberg pointed out. Despite accumulating evidence, she noted, blood clots are not listed as a potential side effect of antipsychotic drugs.

(From Reutershealth)