PHOTOTOXICITY CAUSED BY HYPERICUM

Cell cultures of human keratinocytes were incubated with known photose nsitating substances (psoralene, chlorpromazine, hypericin) or with hy pericum extract. After 24 hours a defined UVA-treatment was supplied a nd subsequently the vitality of the cells measured in correlation to t he concentration of the substances. The LC(50) was most clearly reduce d by the addition of 5-methoxypsoralene and hypericin, while hypericum extracts showed only a mild effect. A quantitative correlation of suc h findings in human beings is only possible when the results from anim al toxicology have been concluded. These data indicate that the usual therapeutic doses of hypericum extracts are about 30 to 50 times below the level of phototoxicity.