The Hospice Clinician Blog

AstraZeneca is adding a new warning to the labels of Seroquel and Seroquel XR. The revised label says Seroquel and Seroquel XR “should be avoided” in combination with other drugs that are known to prolong the cardiac QT interval, including methadone. Other medications to avoid include some antipsychotics (ziprasidone, chlorpromazine, thioridazine), some quinolone antibiotics (levofloxacin, gatifloxacin), and all class IA and class III antiarrhythmics (including amiodarone). According to the FDA, the purpose of the revised labeling is to caution prescribers, and should not be considered a complete ban against prescribing Seroquel with these other medications.

In clinical trials, Seroquel was not associated with a persistent increase in QT intervals, but the QT effect was not systematically evaluated in a thorough QT study. In post-marketing experience, there have been cases of QT prolongation in patients who overdosed on Seroquel, in patients with concomitant illness, and in patients taking medicines known to cause electrolyte imbalance or increase QT interval. Previously, Seroquel labeling cautioned against the risk of QT prolongation, but did not list specific medications to avoid in combination.

According to FDA representatives, the label was changed after the FDA received new information about reports of arrhythmia in 17 patients who took more than the recommended dose of Seroquel. Though it should not be a problem at the recommended dosage, it may still be good advice to avoid using Seroquel in combination with agents that prolong the QT interval.

Seroquel should also be avoided in circumstances that may increase the risk of occurrence of torsades de pointes, including a history of cardiac arrhythmias such as bradycardia, and hypokalemia or hypomagnesemia. Caution should be exercised when Seroquel is prescribed in patients at increased risk of QT prolongation (e.g. cardiovascular disease, family history of QT prolongation, the elderly, congestive heart failure and heart hypertrophy).

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