St John's wort and anticonvulsants

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St John's wort interacts with some anticonvulsants (carbamazepine, phenobarbitone, phenytoin) and leads to reduced blood levels of the anticonvulsant with consequent risk of seizures.

Suggested management of patients already taking SJW preparations:

  • check anticonvulsant levels and stop SJW
  • note that anticonvulsant levels may increase on stopping SJW
  • it may be necessary to adjust the dose of the anticonvulsant


  • CEM/CMO/2000/4

Last reviewed 01/2018