Flecainide and Fluconazole: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fluconazole
Flecainide
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
An increased risk of QT interval prolongation
Interaction Deep Dive
Concomitant use of fluconazole and QT prolonging agents increases the risk of QT interval prolongation12. Prior to use of azole antifungals (including fluconazole), consider substituting or discontinuing medications that increase risk of QTc prolongation, if possible 3.
Why it happens (mechanism)
Additive QT interval prolongation
Literature reports
2 reports — tap to read
a) QTc prolongation due to azole antifungals with or without other potentially contributory medications was evaluated in a case series (N=16 cases). QTc prolongation occurred more frequently in younger (median age, 29 years; interquartile range (IQR), 15.8 to 45 years) and female (75%) patients. Fluconazole was the most frequently administered antifungal drug (10 cases); voriconazole and liposomal amphotericin B were administered in 6 and 4 cases, respectively. QTc prolongation occurred at a median duration of 5 days (IQR, 4.5 to 11 days) from azole administration. Longest QTc interval was a median of 551 milliseconds (IQR, 515 to 590 milliseconds). Torsade de pointes occurred in 81% with QTc prolongation. QTc interval returned to within the normal range after intervention for QTc prolongation in a median of 7 days (IQR, 3.5 to 18 days). Recurrence of QTc prolongation after re-administration of azole treatment was observed in 2 cases attributed to fluconazole or voriconazole. Concomitant medications potentially contributing to QTc prolongation were administered in 75%; the most common was concomitant use of antibiotics in 50%, followed by antidepressants and proton pump inhibitors present 33% each 3.
b) Case reports have described QT prolongation and torsades de points associated with fluconazole 345.
Common questions
Can I take Flecainide and Fluconazole together?
An increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Flecainide and Fluconazole interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
- Fluconazole Dosing For 'Intestinal Candida'
- Eliquis With Fluconazole Drug Interaction
- Can You Cut Or Split Fluconazole In Half?
- Is the Magnesium Stearate in Flecainide Animal or Vegetable Based?
- Is It Safe to Take Lutein and Zeaxanthin With Flecainide?
- Is Black Seed Oil Safe With Metoprolol And Flecainide?
Questions for your pharmacist
- Does my dose of Flecainide or Fluconazole need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (5)
- Product Information: DIFLUCAN(R) oral tablets, suspension, fluconazole oral tablets, suspension. Roerig (per FDA), New York, NY, 2024. DailyMed
- Product Information: DIFLUCAN(R) intravenous injection, fluconazole intravenous injection. Roerig (per FDA), New York, NY, 2024. DailyMed
- Kitaya S, Nakano M, Katori Y, et al: QTc interval prolongation as an adverse event of azole antifungal drugs: case report and literature review. Microorganisms 2024; 12(8):1619. PubMed
- Khazan M & Mathis AS: Probable cause of torsades de pointes induced by fluconazole. Pharmacotherapy 2002; 22(12):1632-1637.
- Wassmann S, Nickenig G, & Bohm M: Long QT syndrome and torsade de pointes in a patient receiving fluconazole. Ann Intern Med 1999; 131:797. PubMed
Keep reading about Fluconazole
Keep reading about Flecainide
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist