Metronidazole with Ketoconazole Interaction Details
Brand Names Associated with Metronidazole
- Flagyl®
- Flagyl® 375
- Flagyl® ER
- Metronidazole
Brand Names Associated with Ketoconazole
- Ketoconazole
- Nizoral®
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Jan 04, 2024
Interaction Effect
An increased risk of QT interval prolongation
Interaction Summary
MetroNIDAZOLE can cause QT prolongation and has caused torsades de pointes with concomitant amiodarone administration . Susceptible patients may require ECG monitoring and avoidance of medications known to cause QT prolongation .
Severity
Major
Onset
Unspecified
Evidence
Theoretical
How To Manage Interaction
MetroNIDAZOLE can cause QT interval prolongation and has caused torsades de pointes with concomitant administration of another QT-interval prolonging drug . Susceptible patients may require ECG monitoring and avoidance of medications known to cause QT prolongation .
Mechanism Of Interaction
Additive QT interval prolongation
Literature Reports
A) A 71-year-old woman developed QT prolongation 2 days after initiation of IV metroNIDAZOLE for nosocomial pneumonia. She was admitted with atrial fibrillation, and QTc was 396 msec. Medical history included COPD, diabetes, mellitus, hypertension, coronary artery disease, and QT prolongation with moxifloxacin. She received diuretics, ACE inhibitors, omeprazole, and bronchodilators and developed nosocomial pneumonia. Two days after initiation of metroNIDAZOLE, QTc was 559 msec and T waves were inverted. MetroNIDAZOLE was discontinued and ECG returned to normal within 48 hours .
B) A 90-year-old woman with no known history of structural heart disease developed QT prolongation after metroNIDAZOLE treatment for aspiration pneumonia. QTc was 324 msec on admission and 703 msec the next day, after initiation of cefTRIAXone 1 g/day IV and metroNIDAZOLE 500 mg 3 times daily. MetroNIDAZOLE was discontinued and QTc gradually returned to initial value without significant arrhythmias. The patient was advised to avoid medications known to cause QT prolongation .
C) A 71-year-old woman with antibiotic-induced pseudomembranous colitis developed ECG QTc interval prolongation and torsades de pointes with concurrent amiodarone 450 mg bolus followed by 900 mg/day IV and metroNIDAZOLE 1500 mg/day oral administration. Baseline QTc interval was 440 msec. Amiodarone was added after atrial fibrillation developed with 3 days of amiodarone therapy. Conversion to sinus rhythm occurred 2 days later; however, the follow-up ECG revealed a QTc interval of 625 msec. Symptoms progressed to sustained torsades de pointes-variant ventricular tachycardia that required emergent cardioversion/defibrillation to restore normal sinus rhythm. Amiodarone and metroNIDAZOLE were immediately withdrawn, and the QTc interval slowly returned to baseline values without further clinically significant arrhythmia events .
Metronidazole Overview
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Metronidazole capsules and tablets are used to treat infections of the reproductive system, gastrointestinal (GI) tract, skin, heart, bone, joint, lung, blood, nervous system, and other areas of the body. Metronidazole capsules and tablets are also used to treat sexually transmitted diseases (STDs). Metronidazole extended-release (long-acting) tablets are used to treat bacterial vaginosis (an infection caused by too much of certain types of harmful bacteria in the vagina) in women. Metronidazole is in a class of medications called nitroimidazole antimicrobials. It works by stopping the growth of bacteria.
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Antibiotics will not work for colds, flu, or other viral infections. Using antibiotics when they are not needed increases your risk of getting an infection later that resists antibiotic treatment.
Ketoconazole Overview
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Ketoconazole is used to treat fungal infections when other medications are not available or cannot be tolerated. Ketoconazole should not be used to treat fungal meningitis (infection of the membranes surrounding the brain and spinal cord caused by a fungus) or fungal nail infections. Ketoconazole is in a class of antifungals called imidazoles. It works by slowing the growth of fungi that cause infection.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.