A red flag has been raised once again over the safety of Sanofi-Aventis antibiotic Ketek, after the company suspended a clinical trial of the drug in children

Last month, the US Food and Drug Administration (FDA) said it was considering adding a warning label to Ketek (telithromycin) after a review linked the drug to 12 cases of liver failure and four deaths. But Sanofi said that the halt in testing had not been sought by the agency and was unrelated to the safety concerns.

Ketek has come under scrutiny from senior US politicians, including Republican Senator Charles Grassley who maintains that the FDA should never have approved the drug because of “unresolved questions regarding the drug's safety and efficacy, and ... knowledge that some of the clinical safety data supporting its approval was fraudulent.”

Sanofi said in a statement that the trials had been suspended ‘pending confirmation ... that [they] are consistent with the current thinking of the FDA.”

At the start of the year, the agency said that reports of liver damage in patients taking Ketek had prompted an investigation to assess whether to add a warning of this possible side effect. Meanwhile, the European Medicines Agency (EMEA) has also tightened up the drug’s labelling to warn of liver side effects.

Ketek is already approved for treating respiratory tract infections in adults, but the paediatric studies were investigating its use in childhood diseases such as tonsillitis and ear infections.

Sanofi-Aventis has not reported Ketek sales since the third quarter of 2005, when it posted a 7.3% decline in turnover to 38 million euros ($47m) year-on-year, and the antibiotic is a minor product for the company despite once-touted as a potential blockbuster.