In May 2006, the FDA recommended that a black box warning be added to the Ketek label, stating that “severe, life-threatening, and in some cases fatal” liver toxicity has been reported in patients taking the drug. The recommendation came after FDA safety reviewers found that Ketek has been linked to 12 cases of liver failure, including four deaths, in the U.S. In some cases, liver damage worsened rapidly and happened after just a few doses of Ketek.