The FDA is clarifying dosing and warning recommendations for citalopram hydrobromide (Celexa, Forest Laboratories). There is the possibility that high doses of the antidepressant can cause dangerous abnormalities in the electrical activity of the heart.

The drug label has been changed to describe the caution that needs to be taken when citalopram is used in patients with certain underlying heart conditions, and those who are predisposed to having low levels of potassium and magnesium in the blood. The revised drug label also describes lower doses that should be used in patients over the age of 60. 

Changes in the electrical activity of the heart can lead to the risk of fatal abnormal heart rhythm; because of this risk in certain circumstances, healthcare providers may need to regularly monitor the heart—or check blood levels of potassium and magnesium—in patients who must use Celexa. The maximum recommended dose of Celexa is 20 mg per day for patients older than 60 years of age.

Due to these revelations, the FDA made these recommendations for healthcare professionals:

• Celexa causes dose-dependent QT interval prolongation, which can cause Torsades de Pointes, ventricular tachycardia and sudden death.

• Celexa is not recommended for use at doses greater than 40 mg per day because such doses cause too large an effect on the QT interval and confer no additional benefit.
• Celexa is not recommended for use in patients with congenital long QT syndrome, bradycardia, hypokalemia or hypomagnesemia, recent acute MI or uncompensated heart failure. Celexa use also is not recommended in patients who are taking other drugs that prolong the QT interval.
• The maximum recommended dose of Celexa is 20 mg per day for patients with hepatic impairment, patients who are older than 60 years of age, patients who are CYP 2C19 poor metabolizers or patients who are taking concomitant cimetidine (Tagamet) or another CYP2C19 inhibitor, because these factors lead to increased blood levels of Celexa, increasing the risk of QT interval prolongation and Torsade de Pointes.
• Electrolyte and/or ECG monitoring is recommended in certain circumstances: Consider more frequent ECG monitoring in patients for whom Celexa use is not recommended, but is, nevertheless, considered essential. Patients at risk for significant electrolyte disturbances should have baseline serum potassium and magnesium measurement, with periodic monitoring. Hypokalemia and/or hypomagnesemia may increase the risk of QTc prolongation and arrhythmia and should be corrected prior to initiation of treatment with periodic monitoring.
• Celexa should be discontinued in patients found to have persistent QTc measurements greater than 500 ms.
• Advise patients on Celexa to contact a healthcare professional immediately if they experience signs and symptoms of an abnormal heart rate or rhythm (e.g., dizziness, palpitations or syncope). If patients experience symptoms, the prescriber should initiate further evaluation, including cardiac monitoring.