Researchers have found a higher rate of benign tumors of the pituitary gland and related health problems among patients taking the antipsychotic drug risperidone than in those taking similar drugs.

		Related coverage Four-day biotech conference: It's all about networking Costs of bipolar disorder to society are high

The findings, posted yesterday at the Sixth International Conference on Bipolar Disorder here, were developed by sifting through more than 2 million reports of adverse drug reactions.

Doctors yesterday emphasized that the side effects appear to be uncommon and that the findings need to be confirmed by other studies. Patients should continue taking risperidone unless their doctors advise otherwise, they said.

Still, the results suggest cause for concern, said Dr. Michael Thase, a psychiatrist at the University of Pittsburgh School of Medicine. "The association appears to be too strong to be a chance finding."

Researchers at the Food and Drug Administration and Duke University found 64 reports of pituitary tumors in patients taking certain antipsychotic drugs. Forty-eight of those reports involved patients taking risperidone, marketed as Risperdal.

Reports involving other antipsychotic drugs included eight for Haldol, six for Zyprexa, four each for Geodon and Clozaril, and one for Seroquel.

The totals exceed 64 because some patients took multiple drugs.

Doug Arbesfeld, a spokesman for Janssen Pharmaceutica, which markets Risperdal, said the company would analyze the findings "and other data to determine if further study is required. We're definitely taking it seriously."

Dr. Paul Seligman, who directs the FDA's office overseeing postmarketing drug surveillance, said the agency planned to follow up by reviewing the cases and considering whether modifications should be made to drug labels to inform physicians and patients about tumors or other potential health conditions.

Thase said the tumors often can be shrunk with medication. If they grow too large, they can put pressure on the optic nerve or cause other problems.

The FDA said it began investigating the issue after receiving reports associating antipsychotic drugs with pituitary tumors and increased secretion of prolactin, a pituitary hormone that mainly regulates breast milk production and preparing the body for pregnancy.

Reports also indicated abnormal secretion of breast milk in some patients, which can be caused by increased production of the hormone.

Antipsychotic drugs are known to block dopamine, a chemical neurotransmitter in the brain that acts as a brake on the secretion of prolactin. Studies in mice have suggested that treating them with Risperdal or other antipsychotics can result in tumor growth.

Besides the pituitary tumors, the findings yesterday linked reports of menstrual problems, abnormal milk production and high levels of prolactin to Risperdal compared to other antipsychotic drugs.

The findings were based on "data mining," a technique developed at the FDA to help identify potential drug safety problems in large data bases.

The study, led by the FDA's Dr. Ana Szarfman, used a computer analysis to assess reports of adverse drug reactions reported to the agency since 1968. Of the 307 reports of pituitary tumors, 21 percent occurred in patients taking the antipsychotic drugs.

The findings have limitations. They don't prove, for example, that the tumors were caused by Risperdal or other drugs. And they don't account for the fact that some antipsychotic drugs are used more than others or have been available longer.

Still, the findings suggest that patients taking the drugs who develop abnormal milk production may want to seek medical treatment to determine if their prolactin levels are high, said Dr. P. Murali Doraiswamy, a co-investigator and director of psychiatry clinical trials at Duke University. If they are, an MRI scan may be advisable to assess whether tumors are present, he said.