Phototoxicity

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Phototoxic reaction of the area around the eyes of a lamb from St. John's herbs
Phototoxic reaction on a human leg at ketoprofen treated sites

Phototoxicity is a property of pharmaceutical and chemical substances. It describes the strength with which a substance triggers poisoning (toxic) effects on the surface of the skin when exposed to sunlight . If sunlight does not change the chemical structure of the substance, it is called photostable.

description

Active ingredients of medicaments for the treatment of skin diseases (. E.g. isotretinoin ) act phototoxic, as their active ingredients by UVA and UVB - radiation are chemically modified sunlight.

The toxic effect manifests itself in various symptoms . The skin reacts primarily with reddening, itching, dehydration and flaking.

Some herbal active ingredients can also have a phototoxic effect at high concentrations. So is z. For example , an increased sensitivity of the skin to light has been observed in patients who regularly take St. John's wort preparations as an antidepressant .

Causes of Phototoxicity

Chemical bonds can be destroyed by high-energy UVA radiation , among other things , if the energy of the radiation is greater than the bond energy between the atoms of a substance. This can lead to a comprehensive release of toxic or irritating substances from originally low / non-toxic substances. Chemical activation of the substances by supplying energy from light is also possible (e.g. heating). In this way, for example, substances such as psoralen can bind to the DNA molecules in the cell nucleus (in the case of psoralen a cycloaddition takes place) or split them, whereby the cell can die or the immune system triggers inflammatory reactions to destroy the damaged cell or to defend against the foreign substance, from which the symptoms such as itching or rash result.

Phototoxic substances in everyday life

Furocoumarins , which are often found in umbellifers such as hogweed ( giant hogweed , meadow hogweed ), bergamot , angelica ( angelica ) and in a number of other plants, as well as the fagopyrin of buckwheat ( buckwheat disease ) can cause phototoxic reactions.

Ignoring these plants leads to symptoms of poisoning in people who have recently worked with the plants and have come into contact with their secretions.

List of phototoxic substances

See also

literature

  • Lutz Roth, Kurt Kormann and a .: Poisonous plants - plant poisons. Occurrence, effect, therapy, allergic and phototoxic reactions; new: with a special section on poisonous animals. 5th enlarged edition. Nikol, Hamburg 2008, ISBN 978-3-86820-009-6 .

Individual evidence

  1. ↑ G. Weimark, E. Nilsson: Phototoxicity in Heracleum sphondylium. In: Planta medica. Volume 38, No. 2, 1980, pp. 97-111.
  2. ↑ New photodegradation pathways for Naproxen, a phototoxic non-steroidal anti-inflammatory drug . In: Journal of Photochemistry and Photobiology A: Chemistry . tape 54 , no. 1 , October 1, 1990, ISSN  1010-6030 , p. 131-134 , doi : 10.1016 / 1010-6030 (90) 87018-7 .