Answer
St John's wort can lower phenytoin sodium concentrations in the blood and reduce its clinical effects, so herbal preparations containing St John's wort should not be used while taking phenytoin sodium.
Sources for this answer
- Phenytoin Hospira 50 mg/ml Injection BPHospira UK Ltd · emc · SmPC §4.4 Special warnings and precautions for use · Version 25Document updated
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