Warfarin and Linezolid Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Warfarin
Linezolid Injection
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
Concomitant use of linezolid with warfarin increased the PT/INR from 1.62 to 3 in one retrospective survey2 and reduce warfarin dose requirements from 3.23 mg/day to 2.69 mg/day in another retrospective study. Consider close PT/INR monitoring during 1 and after concomitant use 2.
Why it happens (mechanism)
Unknown
Literature reports
2 reports — tap to read
a) In a retrospective study (N=16), addition of linezolid to warfarin therapy for anticoagulation in patients using a left ventricular assist system for severe heart failure significantly reduced the mean warfarin dose from 3.23 mg/day (7 days prior to initiation of linezolid) to 2.69 mg/day (10 days after linezolid initiation). The mean PT/INR was increased, but the difference was nonsignificant. Linezolid was administered as 1200 mg/day for more than 7 days in 14 patients orally and in 2 patients intravenously 1.
b) In patients who had undergone heart surgery and were treated with warfarin to prevent postoperative thrombosis, addition of linezolid to treat heart-related infection significantly increased the PT/INR from 1.62 prior to addition of the antibiotic to 3 following 4 to 5 days of concomitant use (N=5). Over the course of the week following discontinuation of linezolid, the PT/INR was significantly decreased from 1.65 to 1.26 in 5 patients due to warfarin dosage adjustment or drug withdrawal. The mean duration of linezolid use was 27.3 days and the dose was 600 mg every 12 hours 2.
Common questions
Can I take Warfarin and Linezolid Injection together?
Increased INR Always confirm with your pharmacist or prescriber before making any change.
How serious is the Warfarin and Linezolid Injection 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 "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Warfarin or Linezolid Injection 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 (2)
- Kinoshita S, Wada K, Matsuda S, et al: Interaction between Warfarin and Linezolid in Patients with Left Ventricular Assist System in Japan. Intern Med 2016; 55(7):719-724. PubMed
- Sakai Y, Naito T, Arima C, et al: Potential drug interaction between warfarin and linezolid. Intern Med 2015; 54(5):459-464. PubMed
Keep reading about Warfarin
Keep reading about Linezolid Injection
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