Many drugs may cause QT prolongation, which can lead to TdP and resulting sudden cardiac death. The following drugs are included: 

- Antiarrhythmics: procainamide, quinidine, amiodarone, flecainide, propofenone, disopyramide, dronedarone, sotalol, dofetilide, ibutilide
- Antihistamines: terfenadine, astimazole
- Antipsychotics: quetiapine, haloperidol, clozapine
- Tri- and tetra-cyclic antidepressants: imipramine, doxepin
- Selective serotonin reuptake inhibitors: citalopram, fluoxetine
- Antimicrobials: ciprofloxacin, levofloxacin, moxifloxacin, gatifloxacin, ofloxacin, erythromycin, clarithromycin, azithromycin
-Antifungals: ketokonazole, voriconazole
- Antimalarials: quinine, mefloquine, chloroquine

Kalamazoo College

Long QT syndrome refers to the prolongation of a patient's QT interval, at greater than 450 milliseconds for men and greater than 470 milliseconds for women. At intervals above 500 milliseconds, the risk of cardiac events is significantly multiplied as QTc prolongation predisposes individuals to ventricular tachyarrhythmias like TdP, ventricular fibrillation, and resulting death. LQTS may be inherited, or acquired due to drug effects or electrolyte changes.

Long QT Syndrome (LQTS)

Ambhore, A., Teo, S. G., Omar, A. R. B., & Poh, K. K. (2014). ECG series: Importance of QT interval in clinical practice. Singapore Medical Journal, 55(12), 607. https://doi.org/10.11622/smedj.2014172

ECG Series: Importance of QT Interval in Clinical Practice

Drugs Associated with LQTS/QT Prolongation/TdP

Ventricular tachycardia is an arrhythmia in which the heart's lower chamber beats too quickly, improperly distributing oxygenated blood. It can lead to chest palpitations, low blood pressure, chest pain, shortness of breath, fainting, dizziness and lightheadedness, or even cardiac death via ventricular fibrillation.

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