Apixaban, rivaroxaban, edoxaban and dabigatran rely to varying degrees on CYP3A4 and P-glycoprotein. Strong inducers of these pathways lower DOAC levels, and product labels advise avoiding the combination.
Warfarin is also affected by inducers but can be monitored and titrated with the INR.
- Strong inducers include carbamazepine, phenytoin, phenobarbital, primidone and rifampicin.
- St John's wort is also a strong inducer and is easily missed.
- Ask about drugs prescribed by other specialists, especially neurology and TB clinics.
- Rifampicin-based TB treatment is common in India and is a frequent cause of this interaction.
Why it matters
DOACs have no routine monitoring, so an inducer can quietly leave a patient unprotected.
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