What are the risks of taking olanzapine (olanzapine), seroquel (quetiapine), and plaquenil (hydroxychloroquine) together for 4 weeks with a normal baseline QTc (QT interval corrected)?

Risk of QT Prolongation with Combined Olanzapine, Quetiapine, and Hydroxychloroquine

The combination of olanzapine, quetiapine, and hydroxychloroquine presents a significant risk of QTc prolongation that could lead to torsade de pointes, even with a normal baseline QTc interval. 1

QT Prolongation Risk Assessment

• Each medication individually carries QT prolongation risk:

  • Olanzapine: Associated with QT prolongation of approximately 4-6 ms 2
  • Quetiapine: Known to prolong QTc interval 1, 3
  • Hydroxychloroquine: Causes moderate QT prolongation 1

• The combination of multiple QT-prolonging medications significantly increases the risk of reaching clinically dangerous QTc levels, even when starting from a normal baseline 4

• Antipsychotic polytherapy has been shown to cause significant QTc prolongation (mean increase of 24 ± 21 ms) compared to monotherapy 4

Specific Risks of This Combination

• The European Society of Cardiology specifically warns against the combination of QT-prolonging drugs as it increases the risk of torsade de pointes 1

• Hydroxychloroquine is specifically listed as interacting with antipsychotics to increase QT prolongation risk 1

• While olanzapine has a lower risk of QT prolongation compared to some antipsychotics, studies show it still carries a 15.38% risk of QTc prolongation 5

• Quetiapine has been associated with QT prolongation, particularly when combined with other medications 1, 3

Monitoring Recommendations

• ECG monitoring is essential:

  • Baseline ECG before starting treatment 6, 7
  • Follow-up ECG after 2 weeks of combined therapy 1
  • Additional ECG monitoring if symptoms develop (palpitations, syncope, dizziness) 7

• Electrolyte monitoring:

  • Check potassium, magnesium, and calcium levels at baseline 6, 7
  • Maintain potassium >4 mmol/L and magnesium >2 mmol/L 6
  • Repeat electrolyte measurements monthly during the 4-week treatment period 1

Risk Mitigation Strategies

• Consider alternative medications with lower QT prolongation risk if possible 3

• If this combination is absolutely necessary:

  • Use the lowest effective doses of each medication 1, 7
  • Avoid other QT-prolonging medications 1
  • Correct any electrolyte abnormalities promptly 6, 7
  • Consider telemetry monitoring if QTc exceeds 480 ms 6

• If QTc increases to >500 ms or by >60 ms from baseline, medication discontinuation should be considered 6, 7

Special Considerations

• The risk is heightened in patients with:

  • Electrolyte abnormalities (especially hypokalemia, hypomagnesemia) 6
  • Structural heart disease 7
  • Advanced age 7
  • Female gender 7

• The 4-week duration may reduce the risk compared to longer-term use, but significant QTc prolongation can occur within the first few days of treatment 5