Can Seroquel (quetiapine) prolong the QT interval?

Quetiapine and QT Interval Prolongation

Yes, Seroquel (quetiapine) can prolong the QT interval, with an average prolongation of approximately 6 ms. 1

Quetiapine's Effect on QT Interval

Quetiapine has been documented to cause QT interval prolongation, though to a moderate degree compared to other antipsychotics. According to clinical guidelines, quetiapine causes an average QT prolongation of 6 ms 1. While this is more than medications like aripiprazole (0 ms) or olanzapine (2 ms), it is less concerning than high-risk antipsychotics such as thioridazine (25-30 ms) or ziprasidone (5-22 ms) 1.

The FDA label for quetiapine specifically addresses QT prolongation:

• Quetiapine was not associated with persistent QT prolongation in clinical trials
• However, QT prolongation has been reported in post-marketing cases, particularly in:
  • Overdose situations
  • Patients with concomitant illnesses
  • Patients taking other medications known to affect electrolyte balance or increase QT interval 2

Risk Factors for QT Prolongation with Quetiapine

The risk of clinically significant QT prolongation with quetiapine increases with:

1. Concomitant medications: Using quetiapine with other QT-prolonging drugs significantly increases risk 1, 2, 3

   • Class 1A antiarrhythmics (quinidine, procainamide)
   • Class III antiarrhythmics (amiodarone, sotalol)
   • Other antipsychotics (ziprasidone, chlorpromazine, thioridazine)
   • Certain antibiotics (gatifloxacin, moxifloxacin)

2. Patient-specific factors 1, 2:

   • Female sex
   • Age >65 years
   • Cardiovascular disease
   • Family history of QT prolongation
   • Congestive heart failure
   • Heart hypertrophy
   • Electrolyte abnormalities (hypokalemia, hypomagnesemia)
   • Bradycardia

3. Overdose situations: Case reports document significant QT prolongation with quetiapine overdose 4, 5

Clinical Implications and Monitoring

When prescribing quetiapine, the following precautions should be taken:

• Baseline assessment:

  • Obtain baseline ECG before starting treatment 1
  • Check electrolyte levels (particularly potassium and magnesium) 1

• Ongoing monitoring:

  • Repeat ECG 7 days after initiation and after any dose changes 1
  • Manually measure QT interval rather than relying on automated readings 1
  • Monitor electrolytes regularly 1, 2

• Risk mitigation:

  • Avoid combining quetiapine with other QT-prolonging medications when possible 2
  • Maintain serum potassium between 4.5-5 mEq/L 1
  • Correct any electrolyte abnormalities promptly 1, 2

• When to discontinue:

  • Consider dose reduction or discontinuation if QTc is 470-500 ms (females) or 450-500 ms (males) 1
  • Discontinue if QTc >500 ms 1

Comparative Risk Among Antipsychotics

When QT prolongation is a concern, the relative risk of antipsychotics (from lowest to highest risk) is:

• Aripiprazole (0 ms) and brexpiprazole (no significant prolongation) 1, 6
• Olanzapine (2 ms) 1
• Risperidone (0-5 ms) 1
• Quetiapine (6 ms) 1
• Haloperidol (7 ms) 1
• Clozapine (8-10 ms) 1
• Pimozide (13 ms) 1
• Ziprasidone (5-22 ms) 1
• Thioridazine (25-30 ms) 1

Special Considerations for Critical Care Settings

ICU patients receiving quetiapine require extra vigilance as they often have multiple risk factors for QT prolongation:

• Multiple medications
• Electrolyte disturbances
• Underlying cardiac conditions
• Critical illness itself 7, 3

A study of ICU patients found QTc prolongation >60 ms occurred in 13.6% of patients receiving quetiapine, with concomitant QT-prolonging medications being the most significant risk factor 3.