What are common drugs that prolong the QT (quantum time) interval?

From the Guidelines

Common drugs that can prolong the QT interval include antiarrhythmics, antibiotics, antipsychotics, antidepressants, antiemetics, and antimalarials, with the risk increasing with higher doses and multiple QT-prolonging medications used simultaneously. The list of QT-prolonging drugs is extensive and includes medications such as amiodarone, sotalol, procainamide, azithromycin, erythromycin, clarithromycin, moxifloxacin, levofloxacin, pentamidine, haloperidol, quetiapine, ziprasidone, citalopram, escitalopram, tricyclic antidepressants, ondansetron, domperidone, chloroquine, and hydroxychloroquine 1. These drugs can block potassium channels in heart cells, delaying cardiac repolarization and extending the QT interval, which can increase the risk of dangerous heart rhythm disturbances like torsades de pointes.

• Key factors that increase the risk of QT prolongation and torsades de pointes include:
  • Higher doses of QT-prolonging medications
  • Use of multiple QT-prolonging medications simultaneously
  • Pre-existing heart conditions
  • Electrolyte abnormalities, especially low potassium or magnesium
  • Advanced age
  • Female gender
  • Genetic predisposition
• It is essential to monitor the QT interval with ECGs, maintain normal electrolyte levels, and be vigilant for symptoms like dizziness, palpitations, or syncope that might indicate arrhythmias when prescribing these medications 1.
• The risk-benefit analysis should be considered when using QT-prolonging drugs, and alternative medications with a lower risk of QT prolongation should be chosen when possible 1.
• Healthcare providers should be aware of the potential for QT prolongation and torsades de pointes with these medications and take steps to minimize the risk, such as monitoring ECGs and electrolyte levels, and being cautious when using multiple QT-prolonging medications simultaneously 1.

From the FDA Drug Label

In clinical trials, quetiapine was not associated with a persistent increase in QT intervals. However, the QT effect was not systematically evaluated in a thorough QT study. The use of quetiapine should be avoided in combination with other drugs that are known to prolong QTc including Class 1A antiarrythmics (e.g., quinidine, procainamide) or Class III antiarrythmics (e.g., amiodarone, sotalol), antipsychotic medications (e.g., ziprasidone, chlorpromazine, thioridazine), antibiotics (e.g., gatifloxacin, moxifloxacin), or any other class of medications known to prolong the QTc interval (e.g., pentamidine, levomethadyl acetate, methadone) Hydroxychloroquine sulfate prolongs the QT interval. There may be an increased risk of inducing ventricular arrhythmias if hydroxychloroquine sulfate is used concomitantly with other arrhythmogenic drugs

Common drugs that prolong the QT interval include:

• Hydroxychloroquine sulfate 2 2
• Class 1A antiarrythmics (e.g., quinidine, procainamide) 3
• Class III antiarrythmics (e.g., amiodarone, sotalol) 3
• Antipsychotic medications (e.g., ziprasidone, chlorpromazine, thioridazine) 3
• Antibiotics (e.g., gatifloxacin, moxifloxacin) 3
• Pentamidine 3
• Levomethadyl acetate 3
• Methadone 3

From the Research

Common Drugs that Prolong QT Interval

The following drugs have been associated with QT interval prolongation:

• Antipsychotic drugs, including:
  • Thioridazine, which can cause a QT prolongation of up to 30 ms 4
  • Pimozide, which can cause QT prolongation 4, 5
  • Sultopride, which carries a high risk of arrhythmias related to QT interval prolongation 5
  • Droperidol, which carries a high risk of arrhythmias related to QT interval prolongation 5
  • Haloperidol, which can cause QT prolongation ranging from 4-6 ms 4, 6
  • Quetiapine, which can cause QT prolongation and is associated with greater odds of torsades de pointes ventricular tachycardia, especially in cases of drug overdose 7
  • Risperidone, which can cause QT prolongation ranging from 4 ms and is associated with greater odds of torsades de pointes ventricular tachycardia, especially in cases of drug overdose 4, 7
  • Olanzapine, which can cause QT prolongation ranging from 4-6 ms, but is considered to have negligible effects on the QT interval compared to other antipsychotic agents 4, 6, 5
  • Ziprasidone, which can cause QT prolongation and is associated with an increased risk of ventricular tachycardia 6, 7, 5
• Other drugs, including:
  • Low-potency phenothiazines, such as thioridazine, which have been more often associated with prolonged QTc interval 8
  • High-potency typical antipsychotics, such as fluphenazine and haloperidol, which may also cause prolonged QTc interval 8
  • Atypical antipsychotics, such as iloperidone, which may cause prolonged QTc interval 8

Factors that Increase the Risk of QT Interval Prolongation

The following factors can increase the risk of QT interval prolongation:

• Hypokalemia and hypomagnesemia 4, 6, 5
• Bradycardia 4, 6, 5
• Congenital long QT syndrome 5
• Underlying cardiac pathology 5
• Combination of two or more drugs affecting the same pathway 4, 6
• Genetic predisposition 6