[St. John's wort (Hypericum perforatum L.). A plant with relevance for dermatology].
Saint John's wort (Hypericum perforatum L.) is a herbal remedy that is effective in the treatment of mild to moderate depression. In traditional folk medicine, oily extracts of St. John's wort are used for topical treatment of wounds, burns and myalgia. The lipophilic phloroglucin-derivative hyperforin has antibacterial and antiinflammatory effects. These effects could be of relevance in topical treatment of infected wounds and other dermatoses, but no studies have been conducted so far. The naphtodianthrone hypericin is a photodtodynamic active substance that kills tumor cells via the induction of apoptosis. Hypericin also displays antiviral activity in vitro. In vivo, intravenous or oral treatment with hypericin of HIV-infected subjects did not result in a reduction of the virus load. Most of the patients treated with hypericin experienced phototoxicity. Similar phototoxic symptoms ("hypericism") have been observed in grazing animals ingesting large amounts of St. John's wort. In contrast, antidepressant medication with St. John's wort usually does not produce phototoxic symptoms. Recent pharmacokinetic studies suggest that the phototoxic threshold level of hypericin is not reached with dosages used for the oral treatment of depression. However, very recent reports demonstrated interactions of St. John's wort with other drugs such as digoxin, indinavir and cyclosporin. Blood levels of these drugs were dramatically decreased by St. John's wort. This should be considered in the treatment of skin conditions with antiviral drugs or cyclosporin.