The FDA said it had received reports that the use of Mavyret (glecaprevir/pibrentasvir), Zepatier elbasvir and grazoprevir) or Vosevi (sofosbuvir/velpatasvir/voxilaprevir) to treat chronic hepatitis C in patients with moderate to severe liver impairment has caused rare cases of worsening liver function or liver failure.

The agency said the three drugs are safe and effective in patients with no or mild liver impairment, but they are not indicated for use in patients with moderate to severe liver impairment. In many reported cases, liver failure occurred in patients who had signs and symptoms of moderate to severe liver impairment or other serious liver problems and should not have been treated with the drug, the agency said.

Clinical trials in patients with compensated cirrhosis or mild liver impairment have shown that the medicines are “well tolerated and highly effective,” the agency said. “When prescribed as indicated, these medicines continue to be safe and effective.”