Hepatitis C virus (HCV) regimens containing Gilead Sciences’ Sovaldi (sofosbuvir), including Harvoni (ledipasvir/sofosbuvir), may in rare cases cause an abnormally slow heart rate, HealthDay reports. Writing in a letter to the New England Journal of Medicine, French doctors reported three cases, out of 415 people with hep C treated with Sovaldi–containing regimens, of individuals developing what is known as bradyarrythmia, or slow heart rate.

The people with hepatitis C were all taking Sovaldi with either Daklinza (daclatasvir), Olysio (simeprevir) or ribavirin.

One of the three people who developed a slow heart rate was taking the heart medication Cordarone (amiodarone). In March, Gilead announced that nine people with hep C who took Harvoni or Sovaldi along with Cordarone suffered from low heartbeats, and that one died of a heart attack. Gilead updated its label of the two hep C treatments to caution about the danger of combining Sovaldi with the heart drug.

In response to the New England Journal of Medicine letter, Gilead underlined that bradyarrythmia among those taking Sovaldi–containing regimens is apparently quite rare. More than 13,000 people have participated in clinical trials of a Sovaldi–containing regimen, the response states. Additionally, nearly half a million people have been treated with such a regimen since Sovaldi and Harvoni were approved in 2013 and 2014, respectively.

To read the New England Journal of Medicine letter, click here.

To read the HealthDay article, click here.