The Food and Drug Administration called the approval a step toward "the promise of personalized medicine."
But some medical experts say there could be a downside to approving medicine for specific races of people.
"There are many, many who claim these use of (racial) categories may not have any biological meaning, only social meaning, and basing medical decisions on them may be problematic," said David Magnus, director of the Stanford Medical Center for Biomedical Ethics.
For example, Magnus said, researchers could also look at whether a particular drug worked more effectively on Catholics than Protestants. The more categories explored, the more likely one can find data showing that one category of people is helped more than the others when it comes to a particular medicine, he said.
"But the more we know genetically, the more we know these social categories don't correspond to genetic groups," Magnus said.
FDA officials say that in the case of BiDil, researchers did not start out looking for a drug that worked better for a particular racial group. Two earlier trials of the drug on the general population of severe heart failure patients found no benefit, the FDA said, but they did suggest that BiDil helped the few blacks participating.
Based on those results, NitroMed Inc. of Lexington, Mass., launched a study of 1,050 blacks with severe heart failure. Half of them got standard heart failure drugs and a placebo; the other half got standard drugs plus BiDil. The study showed a 43 percent reduction in deaths and a 39 percent decrease in hospitalizations compared to a placebo, and the study was stopped ahead of schedule last year when doctors saw BiDil clearly was better.
"The information presented to the FDA clearly showed that blacks suffering from heart failure will now have an additional safe and effective option for treating their condition," said Dr. Robert Temple, the agency's associate director of medical policy. "In the future, we hope to discover characteristics that identify people of any race who might be helped by BiDil."
The National Medical Association, which promotes the interests of black physicians and patients in eliminating health disparities, applauded the FDA's decision. The organization also encouraged the scientist involved in testing BiDil to conduct larger clinical trials to see if it would be helpful to other populations.
"It is our hope that BiDil will be brought to market as quickly as possible to enhance its life saving impact," said Dr. Winston Price, president of the National Medical Association. "Any day of delay represents an unacceptable missed opportunity to save lives."
BiDil is a combination of two older drugs, hydralazine and isosorbide dinitrate, neither of which is approved for heart failure. Some common side effects of the drug are headache and dizziness.
Heart failure occurs when the heart is too weak to pump effectively, causing fluid to back up in the lungs - leaving people weak and short of breath. Half die within five years of diagnosis.
Temple said the success of the drug in blacks was a "striking example of how a treatment can help some patients even if it does not help all patients."
Messages left with Lawrence E. Bloch, NitroMed chief financial officer and chief business officer, weren't immediately returned.