Drug interactions
Fluconazole + Metronidazole
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.
Overview
Potential additive QT-interval prolongation with rare risk of torsades de pointes, especially in patients with underlying risk factors (baseline QT prolongation, electrolyte disturbances, structural heart disease) or at higher fluconazole doses.
Mechanism of action
Pharmacodynamic: fluconazole can prolong QT (IKr/hERG blockade); metronidazole has rare associations with QT prolongation. No clinically significant pharmacokinetic interaction is expected.
Clinical management
Avoid in patients with known QT prolongation or uncorrected hypokalemia/hypomagnesemia. If used together in patients with risk factors or with fluconazole ≥400 mg/day, consider baseline and follow-up ECGs, maintain K+ >4 mEq/L and Mg2+ >2 mg/dL, avoid additional QT-prolonging agents, and monitor for palpitations/syncope.
Drug reference
References
- Diflucan (fluconazole) Prescribing Information — FDA Label
- Fluconazole: QT prolongation and torsades risk; interaction considerations — UpToDate
- Fluconazole and Metronidazole – Drug Interaction Monograph — Lexicomp
- Fluconazole – QT/TdP Risk Classification — CredibleMeds
Frequently asked questions
Can I take Fluconazole with Metronidazole?
The interaction is rated: Moderate. Potential additive QT-interval prolongation with rare risk of torsades de pointes, especially in patients with underlying risk factors (baseline QT prolongation, electrolyte disturbances, structural heart disease) or at higher fluconazole doses.
How serious is the interaction between Fluconazole and Metronidazole?
The interaction is rated: Moderate. Evidence level: Low.
How is the interaction between Fluconazole and Metronidazole managed?
Avoid in patients with known QT prolongation or uncorrected hypokalemia/hypomagnesemia. If used together in patients with risk factors or with fluconazole ≥400 mg/day, consider baseline and follow-up ECGs, maintain K+ >4 mEq/L and Mg2+ >2 mg/dL, avoid additional QT-prolonging agents, and monitor for palpitations/syncope.
Why do Fluconazole and Metronidazole interact?
Pharmacodynamic: fluconazole can prolong QT (IKr/hERG blockade); metronidazole has rare associations with QT prolongation. No clinically significant pharmacokinetic interaction is expected.
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