Serotonin reuptake inhibitor Lexapro, or Cipralex, as it’s marketed in Canada, may cause heart rhythm problems. According to Health Canada, risk increases as dosage increases.

Canada will add new warnings to the Cipralex label, stating the active ingredient, escitalopram, may cause electrical charges in the heart known as QT interval prolongation. Labels will also advise the antidepressant should not be taken by patients with congenital long QT syndrome, QT interval prolongation, or a preexisting heart condition. Patients taking antipsychotics, antidepressants, opioid painkillers, and some medications prescribed to treat infections should discuss their Cipralex dosage with their doctor.

At-risk patients like those over age 65, those with liver problems, or those who take certain heartburn medications should take 10 mg per day maximum. Other Cipralex users may continue to take 20 mg per day.

Last August, the U.S. Food and Drug Administration warned that SSRI citalopram, marketed as Celexa in the U.S., may cause similar abnormal heart rhythms at high dosages.

Lexapro was introduced to the U.S. in August of 2002.