The move is the latest in years of maneuvering over Ketek, which has been the subject of a pair of FDA reviews and a U.S. Senate investigation.
Agency officials said Ketek will no longer be approved to treat bacterial sinus infection and bacterial exacerbations of chronic bronchitis, two generally safe upper respiratory tract infections.
It will remain an option for the treatment of community-acquired pneumonia of mild to moderate severity.
John Jenkins, M.D., head of the FDA's office of new drugs, said the agency's decision was "the result of a comprehensive analysis of risks and benefits" of Ketek.
Those risks include liver toxicity, a side effect that has increasingly concerned FDA scientists and industry watchdogs since Ketek gained U.S. approval in April 2004.
An analysis commissioned by the agency late last year found 35 cases of severe injuries that analysts say were likely attributable to Ketek.
Doctors have written an estimated 6 million prescriptions for Ketek since its approval.
But scientists have worried that the risk of liver problems, while rare, may not be worth Ketek's limited benefits.
The drug was never shown to be better than other antibiotics at curing bacterial infections, but was approved under FDA regulations that seek to speed newer agents to market in an effort to combat drug resistance.
Ketek's label was changed in June 2006 to add the warning that it carries a risk of liver damage.
New Ketek Warning
Now, a new boxed warning in Ketek's labeling will warn doctors and consumers that the drug should not be used in patients with myasthenia gravis, a chronic condition that causes muscle to tire and weaken, the agency said.
Sanofi-Aventis, Ketek's manufacturer, said it will alert doctors to the changes and begin distributing patient information guides. Sanofi-Aventis is a WebMD sponsor.
In a statement, the France-based company said Ketek remains "an important option" for doctors.
The FDA has come under scrutiny from Congress over Ketek.
A U.S. Senate committee report in December 2006 concluded the agency had failed to inform expert advisors reviewing Ketek that a large safety study was flawed by researcher misconduct.
And the agency's handling of Ketek is likely to be a key focus of hearings on the agency's practices scheduled for Tuesday in the U.S. House of Representatives.
Jenkins referred to the 2006 episode Monday as "a learning experience for us." If the agency encounters a similar situation in the future, "it's possible we would take a different decision at that point," he said.
Sen. Charles E. Grassley (R-Iowa), whose staff issued the Senate report, said the FDA has been held accountable for its questionable approval of Ketek.
"Now the uses for Ketek are limited, and the public is safer and better informed," Grassley said.
Sanofi-Aventis posted $58.3 million in Ketek sales in the first nine months of 2006, company spokesman Melissa Feltmann tells WebMD.
"I think it's premature to speculate on the exact impact" of Monday's announcement, she says.
SOURCES: John Jenkins, MD, director, Office of New Drugs, FDA. News release, Sanofi-Aventis. Sen. Charles E. Grassley (R-Iowa). Melissa Feltmann, spokesman, Sanofi-Aventis.
By Todd Zwillich
Reviewed by Louise Chang