(Reuters) - U.S. regulators on Monday revised the label for Sanofi SA's heart drug Multaq to reflect a doubling of health risks, including death, for some patients with irregular heart rhythms.
In the updated label, the Food and Drug Administration said Multaq, known chemically as dronedarone, should not be used by patients who have permanent atrial fibrillation (AF), a type of abnormal heart rhythm.
For these types of patients, Multaq doubles the rate of cardiovascular death, stroke and heart failure, the FDA said.
However, the FDA said Multaq is still safe to treat patients with brief bouts of irregular heart rhythm. Doctors should still monitor heart rhythms at least once every three months for all patients taking the drug, the agency said.
In atrial fibrillation, the upper chambers of the heart beat in an uncoordinated manner, which can cause palpitations and shortness of breath. This can also cause blood to pool, raising the risk of blood clots and strokes.
This common condition can be permanent, or short-lived, and is often linked to aging.
In the United States, Multaq is currently only approved for sale for reducing hospitalizations of patients with the temporary version of AF.
But some doctors may still prescribe it off-label for people with permanently irregular heart beats.
The FDA label is meant to ensure the drug goes to the right patients, Sanofi said.
"We're fully committed to patient safety and updating our labels whenever the information comes in that would be useful," said Dr. Paul Chew, U.S. chief medical officer at Sanofi. "We fully agree with the FDA that patients with permanent AF should not use the product."
The U.S. agency's probe into the medicine began in July after data from a halted Sanofi clinical trial showed serious heart problems in patients with permanent AF.
But the FDA said its review of another Sanofi trial showed patients with temporarily irregular heart rhythms should still use the drug.
Europe's medicines regulator also restricted the use of Multaq in September, saying the drug should only be prescribed after alternative treatments have been considered.
About 278,000 people received Multaq prescriptions from U.S. outpatient retail pharmacies from the time the drug was approved for U.S. sale in July 2009 through October of this year, the FDA said. About 1.3 million Multaq prescriptions were given in that period.
Multaq is one of Sanofi's most important new products as it seeks to replace revenue lost when many of its top selling medicines face competition from low-cost generic versions.
About one-third of the company's 2008 sales base will lose patent protection by 2013.
Before the latest problems, many analysts saw Multaq's potential annual sales exceeding $1 billion. Consensus forecasts now point to sales of $573 million in 2016, according to Thomson Reuters Pharma.
Its sales totaled 172 million euros ($224 million) in 2010, including 128 million euros in the United States.
Shares of the company were largely unchanged in afternoon trading on the New York Stock Exchange.
Additional reporting by Elena Berton in Paris; editing by John Wallace and Gerald E. McCormick