QT Interval Prolongation: Medication


To obtain a list of all medications that prolong QT interval in order to determine which drugs can interact with hydroxychloroquine and azithromycin.

Early Findings


  • This document, updated on May 24, 2020, provides a compilation of the drugs associated with QT prolongation.
  • According to Dr Ed Burns, an emergency physician at Prehospital and Retrieval Medicine in Sydney, Australia, the drugs that cause QT prolongation are categorized as follows: antipsychotics, type IA antiarrhythmics, type IC antiarrhythmics, class III antiarrhythmics, tricyclic antidepressants, and other antidepressants.
  • This spreadsheet prepared by the research team can be used to populate the drugs and a brief description for each.

QT Interval Prolongation

  • QT interval prolongation can be caused by certain drugs/medication. TdP is an abnormal heart rhythm, which can cause death. The drugs that prolong the QT interval and TdP are presented in several sources.
  • According to the US Pharmacist, these drugs are described in five different categories: antiarrhythmic agents, antimicrobial agents, antipsychotic agents, antihistamines, antidepressants, and others. Examples of each category are provided below.
    • Antiarrhythmic agents include quinidine, disopyramide, and procainamide, thought to induce TdP as well. The prolonged interval is dependent on the serum level.
    • Antimicrobial agents include ciprofloxacin, levofloxacin, gatifloxacin, and moxifloxacin. These are the most common.
    • Antipsychotic agents include thioridazine, ziprasidone, and droperidol. Similar to the antiarrhythmic agents, these drugs work by blocking the IKr potassium channels. Antihistamines include loratadine, fexofenadine, and cetirizine. These drugs are new versions and do not demonstrate the risk demonstrated by previous drugs in this category that were banned in the US market.
    • Antidepressants include haloperidol, and droeridol.
    • Those that do not fall in the categories above include cisapride, arsenic, and methadone.

Summary of our Early Findings

  • Our initial one-hour research was able to identify various sources that provide a list of these drugs/medication. Our research provides insights from no less than four sources.
  • Our continued research will focus on three different research paths outlined below. Simply select all those that would be relevant to you and your research team will provide a comprehensive research brief.

Proposed next steps:

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