Effect of oral administration of Hypericum perforatum extract (St. John's Wort) on skin erythema and pigmentation induced by UVB, UVA, visible light and solar simulated radiation

Hypericin from St John's wort (Hypericum perforatum L.) is a photosensitizing agent that may cause a severe photodermatitis when higher amounts of St John's wort are ingested by animals. Although Hypericum extracts are widely used in the treatment of depressive disorders, only a little information on the photosensitizing capacity of St John's wort in humans is available. In the present prospective randomized study we investigated the effect of the Hypericum extract LI 160 on skin sensitivity to ultraviolet B (UVB), ultraviolet A (UVA), visible light (VIS) and solar simulated radiation (SIM). Seventy two volunteers of skin types II and III were included and were divided into six groups, each consisting of 12 volunteers. In the single-dose study the volunteers (n = 48) received 6 or 12 coated tablets (5400 or 10 800 mug hypericin). In the steady-state study the volunteers (n = 24) received an initial dose of 6 tablets (5400 mug hypericin), and subsequently 3 x 1 tablets (2700 Kg hypericin) per day for 7 days. Phototesting was performed on the volar forearms prior to medication and 6 h after the last administration of Hypericum extract. The erythema-index and melanin-index were evaluated photometrically using a mexameter. After both single-dose and steady-state administration, no significant influence on the erythema-index or melanin-index could be detected, with the exception of a marginal influence on UVB induced pigmentation (p = 0.0471) in the single-dose study. The results do not provide evidence for a phototoxic potential of the Hypericum extract LI 160 in humans when administered orally in typical clinical doses up to 1800 mg daily. This is in accordance with previous pharmacokinetic studies that found hypericin serum and skin levels after oral ingestion of Hypericum extract always to be lower than the assumed phototoxic hypericin threshold level of 1000 ng/mL. Copyright (C) 2003 John Wiley Sons, Ltd.