Drug interactions
Cefalexin + Warfarin
Severity: Moderate
Cefalexin and Warfarin: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Cephalosporins can occasionally raise the INR in patients taking warfarin, increasing the risk of bleeding. The effect is variable and is more likely during acute infection, poor oral intake or prolonged antibiotic courses.
What this interaction means in plain words
Cefalexin and Warfarin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Cefalexin belongs to Anti Bacterial; Warfarin belongs to Cardiovascular.
Why it happens
Likely reduction of vitamin K producing gut flora and possible effects on vitamin K dependent clotting factor synthesis; the mechanism is not firmly established.
What to do
Check the INR within a few days of starting cefalexin and again after stopping it. Adjust the warfarin dose according to INR and counsel the patient on bleeding signs.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Cefalexin
- Amikacin + Cefalexin Moderate
- Avelumab + Cefalexin Moderate
- Balstilimab + Cefalexin Moderate
- Bcg vaccine live + Cefalexin Moderate
- Cefalexin + Cholera vaccine Moderate
- Cefalexin + Kanamycin Moderate
Other interactions of Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Frequently asked questions
Can I take Cefalexin with Warfarin?
MediHelp rates the interaction as moderate. Cefalexin and Warfarin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Cephalosporins can occasionally raise the INR in patients taking warfarin, increasing the risk of bleeding. The effect is variable and is more likely during acute infection, poor oral intake or prolonged antibiotic courses.
How serious is the interaction between Cefalexin and Warfarin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check the INR within a few days of starting cefalexin and again after stopping it. Adjust the warfarin dose according to INR and counsel the patient on bleeding signs.
What other medicines interact with Cefalexin?
MediHelp also lists interactions of Cefalexin with, for example, Amikacin, Avelumab, Balstilimab. The full list is on the Cefalexin page.
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