St John's Wort (Hypericum perforatum) (all alerts)

St John's Wort (Hypericum perforatum) is an ingredient in complementary medicines which are available without prescription from pharmacies, health food shops, supermarkets, complementary medicine practitioners and other sources. St John's Wort preparations taken by mouth (eg, tablets, capsules or liquids) may interact with some prescription medicines, stopping them from working properly.