Pooling results from three studies, the researchers found that hospitalized patients given nesiritide appeared much more likely to die in the first month after treatment than those given traditional medication such as nitroglycerin or dummy pills.
The intravenous drug has been given to more than 600,000 patients nationwide.
"The public should be very alarmed," said Dr. Jonathan D. Sackner-Bernstein, a cardiologist at North Shore University Hospital in Manhasset, N.Y., and lead author of the study, which appears in Wednesday's Journal of the American Medical Association. He said a large, rigorous study is needed to answer safety questions.
Johnson & Johnson spokesman Mark Wolfe called the analysis inconclusive and said nesiritide is safe and highly effective. Nesiritide, sold as Natrecor, is made by Scios Inc., a Johnson & Johnson subsidiary.
Dr. Robert Temple, director of the Food and Drug Administration's drug evaluation office, said there is "not a convincing case for increased mortality, but we will be looking at all available data."
The researchers acknowledged that the studies were small and not designed to examine increased death risks, so it is possible the results were just a chance finding.