Herbal ingredient St John’s wort may interact with antiepileptics

Patients with epilepsy should not take products that contain St John’s wort as any antiepileptic medicine may interact with St John’s wort.

Article date: November 2007

St John’s wort (hypericum perforatum) is a herbal ingredient commonly available in the UK as an unlicensed herbal medicine.

Traditionally, St John’s wort has had various uses, including external application as a treatment for wounds and burns; it is also taken orally to treat fevers and conditions such as depression.

In 2000, warnings were issued that some antiepileptic medicines interacted with St John’s wort. These warnings were based on the metabolism of these medicines and the known induction and inhibitory effects of St John’s wort on various cytochrome P450 enzymes.

MHRA continues to receive reports of possible interactions with St John’s wort through the Yellow Card Scheme. A recent case involved St John’s wort and several different antiepileptic medicines, which resulted in an increase in the frequency and severity of the patient’s seizures. The antiepileptic medicines the patient was taking (levetiracetam, lamotrigine, and clobazam) were not those previously known to interact with St John’s wort.

The Herbal Medicines Advisory Committee and the Commission on Human Medicines pharmacovigilance expert advisory group have considered the interaction between St John’s wort and antiepileptic medicines by routes other than the recognised cytochrome P450 pathway. Both have recommended that the current warnings about interactions should extend to include all antiepileptic medicines.

Advice for healthcare professionals includes:

  • concomitant use of St John’s wort and antiepileptic medicine is not recommended: healthcare professionals should advise patients with epilepsy not to use products that contain St John’s wort
  • continue to report any suspected adverse reaction with St John’s wort, or any other herbal medicines, through the Yellow Card Scheme

See herbal medicines regulation and safety information.

Article citation: Drug Safety Update November 2007, vol 1 issue 4: 7.

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