Levofloxacin and Acenocoumarol: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acenocoumarol
No brand names on recordLevofloxacin
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
Increased INR
Interaction Deep Dive
INR was increased above therapeutic levels following initiation of levofloxacin for treatment of respiratory infection or pneumonia in elderly patients who had a stable INR of 2 to 3 while receiving long-term anticoagulation with acenocoumarol for atrial fibrillation. Consider more frequent monitoring when concomitant use is required, especially in the elderly and those with renal impairment1.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) INR was increased above therapeutic levels following initiation of levofloxacin in 5 elderly patients who had a stable INR of 2 to 3 on long-term acenocoumarol for atrial fibrillation. Levofloxacin was administered in doses of 500 mg once daily for treatment of respiratory infection (n=2) or pneumonia (n=2), and at a dose of 1000 mg/day in 1 patient with a respiratory infection. Preexisting renal impairment was present in 4 of the 5 patients, and the CrCl in all patients ranged between 23 and 56 mL/min. The maximum INR following 1.5 to 8 days of coadministered acenocoumarol and levofloxacin ranged from 6.78 to 22.4. Acenocoumarol was discontinued in 3 patients, of which 2 received enoxaparin instead. Two patients had 1 dose of acenocoumarol withheld. Vitamin K was administered to all patients, IV in four and orally in one. INR returned to normal in all patients within 12 to 24 hours. The interaction was graded as probable with the Karch-Lasagna algorithm and received a total score of 5 on the Drug Interaction Probability Scale (DIPS) 1.
Common questions
Can I take Levofloxacin and Acenocoumarol together?
Increased INR Always confirm with your pharmacist or prescriber before making any change.
How serious is the Levofloxacin and Acenocoumarol 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.
Questions for your pharmacist
- Does my dose of Levofloxacin or Acenocoumarol 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 (1)
- Palacios-Zabalza I, Bustos-Martinez M, Peral-Aguirregoitia J, et al: Probable interaction between acenocoumarol and levofloxacin: a case series. J Clin Pharm Ther 2015; 40(6):693-695. PubMed
Keep reading about Acenocoumarol
Keep reading about Levofloxacin
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