Health authorities in the U.S. are recommending that doctors keep a close eye on patients taking Ketek for signs of liver problems and to stop treatment if symptoms develop.
The warning follows reports that three patients in North Carolina developed severe liver damage and one of them died, after being treated with Ketek.
But the French drug company Sanofi-Aventis is standing firm and says the drug's safety profile remains unchanged.
They also say that side effects were infrequent and that they were already mentioned in the prescribing information.
The Food and Drug Administration in the U.S. approved the use of Ketek in 2004 for the treatment of acute bacterial bronchitis, sinusitis and pneumonia.
The drug is currently on sale in Europe, Japan and in the U.S.
Sanofi-Aventis, one of the world's largest drugmakers, is in discussions with all health authorities where Ketek is sold and is apparently considering all safety measures and will implement them if needed.
According to doctors at Carolinas Medical Center in Charlotte, North Carolina, a 26-year-old Hispanic man, died two weeks after taking Ketek for five days, while a 51 year-old white woman, needed a liver transplant after taking Ketek.
A third patient, a 46-year-old white man, recovered from drug-induced hepatitis after Ketek therapy was stopped.
All were treated at the North Carolina hospital.
The doctors say the incidents were serious enough to warrant an alert to doctors and further study of the drug's potential to damage the liver.