Drug interactions
Ketoconazole + Moxifloxacin
Severity: Major
Ketoconazole and Moxifloxacin: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Ketoconazole and moxifloxacin both prolong the QT interval, so combined use raises the risk of torsades de pointes. Ketoconazole is also a strong CYP3A4 inhibitor, though moxifloxacin is not metabolized through CYP3A4, so the concern here is additive pharmacodynamics.
What this interaction means in plain words
Ketoconazole and Moxifloxacin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Ketoconazole belongs to Anti Fungals; Moxifloxacin belongs to Anti Bacterial.
Why it happens
Additive blockade of the hERG potassium channel causing delayed repolarization.
What to do
Use an alternative antibiotic or antifungal if possible. If both are necessary, check the baseline QTc, correct electrolytes and repeat the ECG during treatment.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Moxifloxacin
- Amiodarone + Moxifloxacin Contraindicated
- Arsenic trioxide + Moxifloxacin Contraindicated
- Disopyramide + Moxifloxacin Contraindicated
- Dofetilide + Moxifloxacin Contraindicated
- Dronedarone + Moxifloxacin Contraindicated
- Droperidol + Moxifloxacin Contraindicated
Other interactions of Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Frequently asked questions
Can I take Ketoconazole with Moxifloxacin?
MediHelp rates the interaction as major. Ketoconazole and Moxifloxacin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Ketoconazole and moxifloxacin both prolong the QT interval, so combined use raises the risk of torsades de pointes. Ketoconazole is also a strong CYP3A4 inhibitor, though moxifloxacin is not metabolized through CYP3A4, so the concern here is additive pharmacodynamics.
How serious is the interaction between Ketoconazole and Moxifloxacin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use an alternative antibiotic or antifungal if possible. If both are necessary, check the baseline QTc, correct electrolytes and repeat the ECG during treatment.
What other medicines interact with Moxifloxacin?
MediHelp also lists interactions of Moxifloxacin with, for example, Amiodarone, Arsenic trioxide, Disopyramide. The full list is on the Moxifloxacin page.
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