Occlusion (pharmacy)
In galenics, occlusion is the air and water-impermeable covering of skin areas. This leads to a build-up of moisture in the horny layer of the skin ( stratum corneum ) and, as a result, to swelling . The increased water supply facilitates the penetration of many active pharmaceutical ingredients ( active ingredient penetration ). It was first proven in 1954 that higher molecular weight substances penetrate the body through the skin with the help of occlusion. In practice, an occlusion is achieved either with ointments based on hydrocarbons ( e.g. Vaseline ) or wool wax alcohols ( e.g. Unguentum Alcoholum Lanae ) or with plastic occlusive foils .
Usually occlusive methods are used to treat wounds or skin diseases . However, the increased permeability of the skin can also be used to apply pharmaceutical active ingredients for the treatment of other diseases through an active ingredient depot ( transdermal patch ) stuck to the skin .
The mostly oily occlusions form an occlusive layer on the stratum corneum and thus reduce the transepidermal water loss ( TEWL ). In addition, they also act as emollients . A reduction of the transepidermal water loss by more than 40% through occlusions does not make sense, as maceration of the skin with increasing bacterial colonization is the result. Occlusive agents are only effective as long as they remain on the skin; after their removal, the transepidermal water loss increases again to the original values.
Very effective occlusive agents are petroleum jelly (with a water evaporation resistance 170 times higher than that of olive oil ) and mineral oil ( white oil ). The disadvantage of these highly effective occlusive agents, however, is the cosmetically often unacceptable problem of severe "greasiness", so that they are usually only used in combination with other active ingredients.
Other frequently used occlusive substances are paraffin , soybean oil , dimethicone , cyclomethicone , propylene glycol , squalene , beeswax and wool wax.
Dimethicone (2-dimethylsiloxane-glycol-copolymer) acts like cyclomethicone also as an emollient, humectant and stabilizer and can increase the cosmetic acceptance of the product. It is therefore often added to topical dermatological cosmetics today . Since the basic chemical structure of dimethicone corresponds to a silicone oil , it is not without controversy.
literature
- Kurt H. Bauer, Karl-Heinz Frömming, Claus Führer: Textbook of Pharmaceutical Technology. With an introduction to biopharmacy. 7th, revised and expanded edition. Wissenschaftliche Verlags-Gesellschaft, Stuttgart 2002, ISBN 3-8047-1825-6 .
Web links
Individual evidence
- ↑ Alfred Richter: Studies on the permeability of the human skin. Dissertation 1954, Heidelberg.
- ↑ Martina Kerscher: Dermatocosmetics . Springer-Verlag, 2013, ISBN 978-3-662-11456-8 , pp. 81 ( limited preview in Google Book search).