From the Research
Cefazolin can significantly affect International Normalized Ratio (INR) levels, and patients on warfarin therapy who are prescribed cefazolin should be closely monitored for INR levels every day, as there is a high likelihood of developing complications like intracranial hemorrhage. Unlike some antibiotics that have minimal impact on warfarin's anticoagulant effect, cefazolin has been reported to cause INR elevation in several case reports 1, 2. The mechanism behind cefazolin's interaction with warfarin involves its effect on intestinal flora and its structural methyl-thiadiazole side chain, which can result in INR elevation 2.
Some studies have reported that cefazolin can cause significant INR elevation, leading to bleeding complications 1, 2. For example, a case report published in the Journal of pharmacy practice described a patient who developed a significantly elevated INR while receiving cefazolin for osteomyelitis 1. Another case report published in Cureus described a patient who developed intracranial hemorrhage due to cefazolin-induced coagulopathy 2.
While some antibiotics, such as nafcillin, can decrease INR levels by inducing hepatic cytochrome P450 isoenzymes 3, cefazolin has been reported to have the opposite effect. Ceftriaxone, another antibiotic, has also been reported to cause INR elevation 4. However, the interaction between cefazolin and warfarin is more significant, and patients should be closely monitored for INR levels every day 2.
In summary, cefazolin can significantly affect INR levels, and patients on warfarin therapy who are prescribed cefazolin should be closely monitored for INR levels every day. Any patient experiencing unusual bleeding or bruising should contact their healthcare provider immediately, as individual responses can vary 1, 2.