WASHINGTON — An active ingredient in a new heart-failure drug tailored for blacks can increase the risk of developing a form of lupus, a debilitating disease that strikes black women in disproportionately high numbers.

BiDil was officially launched yesterday by NitroMed of Lexington, Mass., as the first drug intended for use by patients in a particular ethnic group. The Food and Drug Administration approved it June 23.

But one of its two key ingredients, a generic compound known as hydralazine hydrochloride, long has been known to cause lupus in some patients, according to FDA documents and interviews with doctors.

One in every 250 black women has lupus, a painful immune-system disorder. Black women are three times more likely to get lupus than white women. Blacks are also more likely than whites to develop congestive heart failure, a weakening of the heart that impairs its ability to pump blood. Heart-failure death rates for black women are nearly twice as high as for white women.

Several cardiologists and lupus specialists agree that the benefits of BiDil appear to clearly outweigh its risks, since heart failure is much more serious than lupus. But some question why FDA-approved prescribing information for BiDil fails to recommend that patients taking the drug get routine blood tests for lupus.

Such tests are recommended for patients taking the generic form of the ingredient in BiDil, hydralazine, when it is prescribed separately.

"I would have rather the product [literature] say that people should have testing every six months," said Dr. Jonathan Sackner-Bernstein, director of clinical research in the heart-failure center at North Shore University Hospital on Long Island, N.Y. He was a member of the FDA advisory panel that voted unanimously to recommend BiDil's approval.

An FDA spokeswoman said the agency stands by its decision. She suggested that decisions about testing are best left to individual doctors.

For some patients, a lack of regular testing could prove hazardous, another physician said.

Dr. Daniel Wallace, a lupus specialist at Cedars-Sinai Medical Center in Los Angeles, said it could backfire on patients who conscientiously take the BiDil but tend to shrug off joint pains, fever and other flulike symptoms that could indicate lupus.

"The problem is going to be the patient who takes the drug as directed and doesn't make the connection," Wallace said. "They'll keep taking the medicine and won't call the doctor." A blood test for lupus antibodies costs about $30, he said.

Doctors should tell patients in advance of the lupus risk, said Wallace, adding, "it's probably good medicine to be tested twice a year."

Indeed, regular testing is recommended in FDA-approved prescribing information for the generic form of hydralazine. It says patients taking the generic should be tested for lupus antibodies before starting on the drug, and "periodically" thereafter.

The prescribing information, also known as the drug "label," guides doctors on how to use a medication and prevent unwanted side effects.

However, prescribing information for BiDil only calls for such testing if a doctor suspects a patient has symptoms of lupus.