Can quetiapine (antipsychotic medication) prolong the QTc (corrected QT) interval?

Quetiapine and QTc Prolongation

Yes, quetiapine does prolong the QTc interval by a mean of 6 milliseconds, which is clinically modest but requires monitoring in high-risk patients. 1

Magnitude of QTc Prolongation

Quetiapine causes a mean QTc prolongation of 6 ms, placing it in the moderate-risk category among antipsychotics. 1 This is:

• 3-fold greater than olanzapine (2 ms) 1
• Similar to risperidone (0-5 ms) 1
• Less than haloperidol (7 ms), clozapine (8-10 ms), or ziprasidone (5-22 ms) 1
• Substantially less than thioridazine (25-30 ms, which carries an FDA black box warning) 1

The FDA label confirms that quetiapine was not associated with persistent QTc increases in clinical trials, but post-marketing cases of QT prolongation have been reported, particularly in overdose situations, patients with concomitant illness, and those taking other QTc-prolonging medications. 2

Clinical Risk Assessment

High-risk situations requiring heightened vigilance include: 1

• Female gender 1
• Age >65 years 1
• Baseline QTc >500 ms 1
• Electrolyte abnormalities (hypokalemia, hypomagnesemia) 1
• Concomitant use of other QTc-prolonging medications 1
• Pre-existing cardiovascular disease 1

In a prospective ICU study, QTc prolongation >60 ms occurred in only 13.6% of critically ill patients receiving quetiapine, with concomitant QTc-prolonging medications being the only significant risk factor (P=0.046). 3 Importantly, there were no cases of torsades de pointes. 3

Evidence Quality and Context

A systematic review of case reports found no cases of quetiapine-induced torsades de pointes or sudden cardiac death among patients using quetiapine appropriately without additional risk factors. 4 Among 12 case reports of QTc prolongation, risk factors included female sex (9 cases), concomitant QTc-prolonging drugs (8 cases), electrolyte abnormalities (6 cases), overdose (5 cases), and cardiac problems (4 cases). 4

A 2025 toxicology workgroup consensus specifically does not recommend continuous cardiac monitoring for acute quetiapine overdose, suggesting the risk of torsades de pointes is likely overstated for this medication. 5 This contrasts with amisulpride, thioridazine, and ziprasidone, where monitoring is recommended. 5

Monitoring Recommendations

Baseline ECG before initiating quetiapine is recommended. 1 Follow-up ECG should be obtained after dose titration. 1

Consider medication adjustment if: 1

• QTc exceeds 500 ms 1
• QTc increases by >60 ms from baseline 1

Monitor and correct electrolytes, particularly potassium and magnesium levels. 1

Medication Selection Algorithm

When QTc prolongation is a concern, the American Academy of Pediatrics and European Heart Journal recommend: 1

First-line alternatives:

• Aripiprazole (0 ms QTc prolongation) 1
• Brexpiprazole (minimal effect) 1

Second-line:

• Olanzapine (2 ms) 1

Third-line:

• Risperidone (0-5 ms) 1
• Quetiapine (6 ms) 1

Avoid if possible:

• Ziprasidone (5-22 ms) 1
• Thioridazine (25-30 ms, FDA black box warning) 1

Critical Caveats

The FDA label specifically warns to avoid quetiapine in combination with: 2

• Class IA antiarrhythmics (quinidine, procainamide) 2
• Class III antiarrhythmics (amiodarone, sotalol) 2
• Other QTc-prolonging antipsychotics (ziprasidone, chlorpromazine, thioridazine) 2
• Certain antibiotics (gatifloxacin, moxifloxacin) 2
• Methadone, pentamidine, levomethadyl acetate 2

Avoid quetiapine in patients with: 2

• History of cardiac arrhythmias (especially bradycardia) 2
• Hypokalemia or hypomagnesemia 2
• Congenital long QT syndrome 2

Exercise caution in: 2

• Cardiovascular disease 2
• Family history of QT prolongation 2
• Elderly patients 2
• Congestive heart failure 2
• Cardiac hypertrophy 2