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Table 5 Top 20 QT drug-drug interaction (QT-DDI) along with their levels, therapeutic class and TdP risks of drugs involved in QT-DDIs

From: Frequency, characteristics and risk factors of QT interval prolonging drugs and drug-drug interactions in cancer patients: a multicenter study

QT-DDIs Therapeutic class TdP riska Levels of QT-DDIsb Frequency
Drug 1 Drug 2 Drug 1 Drug 2 Severity Documentation QT-DDIs: n (%)c
Ondansetron-Prochlorperazine Antiemetic Antipsychotic Known risk of TdP Not included in listsd Major Fair 88 (30.6)
Ciprofloxacin-Ondansetron Antimicrobial Antiemetic Known risk of TdP Known risk of TdP Major Fair 71 (24.7)
Ciprofloxacin-Prochlorperazine Antimicrobial Antipsychotic Known risk of TdP Not included in lists Major Fair 64 (22.2)
Ciprofloxacin-Metronidazole Antimicrobial Antimicrobial Known risk of TdP Conditional risk of TdP Major Fair 10 (3.5)
Ciprofloxacin-Dolasetron Antimicrobial Antiemetic Known risk of TdP Possible risk of TdP Major Fair 6 (2.1)
Dolasetron -Ondansetron Antiemetic Antiemetic Possible risk of TdP Known risk of TdP Major Fair 5 (1.7)
Dolasetron-Metronidazole Antiemetic Antimicrobial Possible risk of TdP Conditional risk of TdP Major Fair 5 (1.7)
Metronidazole-Ondansetron Antimicrobial Antiemetic Conditional risk of TdP Known risk of TdP Major Fair 4 (1.4)
Fluconazole-Metronidazole Antimicrobial Antimicrobial Known risk of TdP Conditional risk of TdP Major Fair 3 (1)
Prochlorperazine-Promethazine Antipsychotic Antiemetic Not included in lists Possible risk of TdP Major Fair 2 (0.7)
Ondansetron-Promethazine Antiemetic Antiemetic Known risk of TdP Conditional risk of TdP Major Fair 2 (0.7)
Metronidazole-Nilotinib Antimicrobial Kinase inhibitor Conditional risk of TdP Conditional risk of TdP Major Fair 2 (0.7)
Dolasetron-Octreotide Antiemetic Antidiarrheal Possible risk of TdP Not included in lists Major Fair 2 (0.7)
Clarithromycin-Ondansetron Antimicrobial Antiemetic Known risk of TdP Known risk of TdP Major Fair 2 (0.7)
Ciprofloxacin-Ketoconazole Antimicrobial Antimicrobial Known risk of TdP Conditional risk of TdP Major Fair 2 (0.7)
Ciprofloxacin-Fluconazole Antimicrobial Antimicrobial Known risk of TdP Known risk of TdP Major Fair 2 (0.7)
Prochlorperazine-Trimethoprim Antipsychotic Antimicrobial Not included in lists Not included in lists Major Fair 1 (0.3)
Prochlorperazine-Sulfamethoxazole Antipsychotic Antimicrobial Not included in lists Not included in lists Major Fair 1 (0.3)
Ondansetron-Tizanidine Antiemetic Muscle relaxant Known risk of TdP Not included in lists Major Fair 1 (0.3)
Nilotinib-Tizanidine Kinase inhibitor Muscle relaxant Conditional risk of TdP Not included in lists Major Fair 1 (0.3)
Metronidazole-Tizanidine Antimicrobial Muscle relaxant Conditional risk of TdP Not included in lists Major Fair 1 (0.3)
Metronidazole-Prochlorperazine Antimicrobial Antipsychotic Conditional risk of TdP Not included in lists Major Fair 1 (0.3)
Metronidazole-Norfloxacin Antimicrobial Antimicrobial Conditional risk of TdP Possible risk of TdP Major Fair 1 (0.3)
  1. AZCERT Arizona Center for Education and Research on Therapeutics, TdP torsades de pointes, QT DDIs QT prolonging drug-drug interactions
  2. aTdP risk was based on AZCERT QT drugs list
  3. bLevels i.e., severity and documentation were based on Micromedex DrugReax® classification
  4. cPercentage calculated in total number of QT-DDIs i.e., 288
  5. dDrugs involved in QT-DDIs were not included in the AZCERT QT drugs lists