January 30, 2013 — The British Medical Journal has published a new study linking the antidepressant medications Celexa (citalopram) and Lexapro (escitalopram) to irregular heart rhythm that could be fatal.
The study results confirm data from previous studies, which prompted FDA warnings in 2011 and 2012. Although the increased risk was small, the researchers found that only Celexa and Lexapro were associated with the disorder. They recommended that doctors should carefully consider this when treating depression in patients at risk of heart problems.
The researchers analyzed data from a large New England hospital system, including data from about 38,400 adult patients were prescribed an antidepressant medication or methadone. All of the patients then had their heart tested with an electrocardiogram between February 1990 and August 2011. The researchers chose to include methadone, an opioid drug, to compare with the antidepressants because methadone is known to affect heart rhythm.
The researchers also found that no other antidepressants besides Celexa and Lexapro were associated with the heart rhythm disturbances. Celexa and Lexapro are actually very similar medications. On a molecular level, Lexapro is a concentrated version of the more-potent half of the Celexa molecule.
The researchers linked Celexa and Lexapro to a small but statistically significant increase in the QT interval — the electrical depolarization and re-polarization period that is normally about 1/3 of a heart beat. A prolonged QT interval can potentially trigger sudden, fatal irregular heart rhythm (arrhythmia). Another risk is torsade de pointes, a type of irregular heart rhythm in which the pumping chambers flutter ineffectively (ventricular fibrillation) and cause sudden cardiac death.
The link between Celexa and irregular heart rhythm is nothing new. The U.S. Food and Drug Administration (FDA) published this Safety Communication in 2011, warning that doctors should not prescribe more than a 40-mg dose of Celexa per day. They were concerned because of the risk of heart rhythm problems and the evidence showing Celexa was not effective at doses greater than 40-mg per day. The FDA also updated their warnings in March 2012 to include expanded guidelines for prescribing Celexa to patients at risk of heart rhythm problems.