Cymbalta's labeling previously noted possible liver problems. The label had warned that "Cymbalta should ordinarily not be prescribed to patients with substantial alcohol use." Now, that warning will read, "Cymbalta should ordinarily not be prescribed to patients with substantial alcohol use or evidence of chronic liver disease," according to a letter to doctors sent by Lilly, Cymbalta's maker.

"It is recommended that Cymbalta not be administered to patients with any [liver] insufficiency," says the FDA.

About a million people have taken Cymbalta since the drug's approval in 2004, according to Lilly's letter. "Among these, several cases of [liver] injury have been spontaneously reported," states Lilly's letter. "Some of these patients had underlying liver disease. Review of these cases suggests that patients with underlying chronic liver disease may be at increased risk of [liver] toxicity with [Cymbalta]," the letter continues.