Stronger WARNINGS about quetiapine and QT prolongation

Watch for the use of multiple medications that can prolong the QT interval, and interactions that can boost levels of these QT drugs....

Introduction

As a clinical pharmacist, you will see stronger warnings about quetiapine (Seroquel, etc) and QT prolongation. Many of the antipsychotics can prolong the QT interval, but not all of them are associated with torsades or sudden death. Torsades with quetiapine is very rare, and usually linked to an overdose. But the problem is that you can't predict who will get it.

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Quetiapine and QT prolongation risks

Identifying high-risk patients

Patients who develop torsades usually have multiple risks, a long QT interval, heart disease, older age, female gender, low serum potassium or magnesium, or slow heart rate.

Watch for the use of multiple medications that can prolong the QT interval, and interactions that can boost levels of these QT drugs.

For example, don't combine quetiapine with other QT prolongers like macrolides (clarithromycin, etc), quinolones (moxifloxacin, etc), tricyclics, Zeldox (ziprasidone), methadone, amiodarone, or quinidine.

Medication considerations

And proceed carefully if patients are on medications that can lower potassium or magnesium, such as diuretics or laxatives, or medications that can slow heart rate, such as beta-blockers.

In risky patients, suggest an alternate antipsychotic, Zyprexa (olanzapine) or Abilify (aripiprazole) aren't known to cause torsades.
Avoid haloperidol, pimozide (Orap Forte), or Neurazine (chlorpromazine) in high-risk patients. These are an even bigger torsades risk than Seroquel. See our note, "Avoid QT-prolonging medications in HIGH-risk patients", for more information.

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References

Alvarez PA, et al. QT alterations in psychopharmacology: proven candidates and suspects. Curr Drug Saf. 2010 Jan;5(1):97-104.
Drew BJ, Ackerman MJ, Funk M, et al. Prevention of torsade de pointes in hospital settings: a scientific statement from the American Heart Association and the American College of Cardiology Foundation. Circulation. 2010;121(8):1047-1060.