From the Guidelines
Augmentin can be used with warfarin, but close monitoring of INR is recommended due to the potential increased risk of bleeding, as evidenced by a prospective study of 120 patients who received a combination of amoxicillin/clavulanate, where patients who received the higher maintenance dose developed a higher proportion of INR values ≥ 4 1. When considering the use of Augmentin with warfarin, it is essential to understand the potential interactions between the two medications. The antibiotic component of Augmentin can alter the gut flora that produce vitamin K, which is important for blood clotting and is affected by warfarin. Additionally, the antibiotic may affect liver metabolism of warfarin, leading to increased anticoagulant effects. Some key points to consider when using Augmentin with warfarin include:
- Monitoring INR more frequently, especially when starting or stopping Augmentin, as the interaction between the two medications can lead to increased anticoagulant effects 1.
- Watching for signs of increased bleeding, such as unusual bruising, nosebleeds, bleeding gums, or blood in urine or stool.
- Informing all healthcare providers about all medications being taken, including warfarin and Augmentin.
- Seeking medical attention immediately if bleeding occurs or if INR values increase significantly. It is crucial to weigh the benefits and risks of using Augmentin with warfarin and to closely monitor patients for any potential adverse effects, as supported by the study published in Circulation: Arrhythmia and Electrophysiology 1.
From the Research
Interaction between Augmentin and Warfarin
- The interaction between Augmentin (amoxicillin/clavulanate) and warfarin can lead to an increased risk of bleeding due to elevated international normalized ratio (INR) levels 2, 3, 4.
- Studies have shown that concomitant administration of amoxicillin/clavulanate and warfarin can result in significant bleeding complications, including hematuria and rectus sheath hematoma 3, 4.
- The mechanism of this interaction is suspected to be related to the decrease in vitamin K-producing gut flora, leading to a vitamin K deficiency 3.
- High doses of amoxicillin/clavulanate (10-12 g daily) have been associated with a higher risk of over-anticoagulation when combined with warfarin compared to normal doses (up to 3.6 g daily) 5.
- Polypharmacy, or the use of multiple medications, can also increase the risk of warfarin-drug interactions and bleeding complications 6, 5.
Clinical Implications
- Patients taking warfarin and prescribed amoxicillin/clavulanate should be closely monitored for signs of bleeding and have their INR levels regularly checked 2, 3, 4.
- Healthcare providers should be aware of the potential interaction between warfarin and amoxicillin/clavulanate and take steps to minimize the risk of bleeding complications, such as adjusting warfarin doses or using alternative antibiotics 6, 5.
- The use of high doses of amoxicillin/clavulanate should be avoided in patients taking warfarin, and alternative treatment options should be considered 5.