Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Patent
1995-04-14
1997-01-28
Isabella, David
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
604305, A61F 1300
Patent
active
055975810
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a foil of chitosan for wound dressing.
Chitosan with the structure formula ##STR1## is a deacetylation product of chitin which can be obtained on a technical scale from the shells of crabs, crawfish and other shell-encased organisms. Chitosan is soluble in diluted solutions or organic acids, for instance in three to five percent acetic acid and can be processed from this solution to foils, plates, gels, sprays and powders, according to known precipitation processes (Manufacturing Chemist 10 (1984) pages 47 to 52).
There are various possibilities to use chitosan as a biocompatible substance in field of medical techniques. From High-Tech 7 (1988) pages 29 to 37 it is known to use chitosan foils for the wound-sealing of burns. On a wounded surface of the human body the foil behaves like a heterologous skin substitute, which not only protects the wound against undesired external mechanical action, but also creates a favorable physiological environment for healing. As a rule the foil is left as a seal on the wound until towards the end of the wound-healing phase the foil is spontaneously rejected. It has also passed through the shrinking process, respectively the reduction process of the wound and has become a kind of scab, underneath of which the injured skin was able to regenerate.
The chitosan foil has a certain air permeability. Through tests which are not part of the prior art it has been found that the oxygen-permeability of the chitosan foil is heavily dependent on the relative humidity of the environment. The oxygen permeability is drastically reduced when the relative humidity decreases. Especially when wounds having a large surface are sealed the sufficient breathing of the wound is not insured. However the gas exchange through a wound dressing is important, because a high CO.sub.2 pressure reduces the pH value and slows down the healing process, and in addition a low oxygen concentration makes possible the proliferation of anaerobic bacteria. Further the use of the known chitosan foil in the dressing of wounds with a large surface is limited due to the fact that the dry foil is relatively brittle. Large-surface wound-sealing on curved body parts, such as elbow, chin, heel, knee or shoulder portions is used rarely or not at all, because of the brittleness of the known chitosan foil.
SUMMARY OF THE INVENTION
It is the object of the invention to indicate a chitosan foil for wound sealing which can be used over large surfaces also in body parts which are generally difficult to dress.
In order to achieve this object the invention teaches that the foil contains glycerin as an elasticizing additive and has a perforated surface which stimulates the gas exchange. According to the invention the foil is provided with breathing openings which are distributed evenly over the surface, in large numbers per surface unit. The diameter of the breathing opening should be larger than 100 .mu.m. The perforations have namely to be so small that the wound secretions can not pass through and be pressed onto the foil surface. The surface has to remain dry and is not allowed to assume a gel-like consistency. The addition of glycerin increases the elasticity of the foil.
According to a preferred embodiment of the invention the foil is charged with an active substance which assists the wound treatment and which is released during the enzymatic decomposition of chitosan. The addition of Australian tea tree oil has proven to be particularly effective. The Australian tea tree oil is obtained through gentle vapor distillation from the leaves of the tea tree (Melaleuca alternifolia). At the same time the etherial oil enhances the bactericidal and fungicidal action of the chitosan. Further it is advantageous when the foil contains cod liver oil as an additional active substance which protects the skin against keratinization, whereby such an additive is also effective against psoriasis.
With the chitosan foil of the invention it is possible to seal wounds caused by skin removal,
REFERENCES:
patent: 4488564 (1984-12-01), Grollier et al.
patent: 4532134 (1985-07-01), Malette
patent: 4572906 (1986-02-01), Sparkes et al.
patent: 4659700 (1987-04-01), Jackson
patent: 4867150 (1989-09-01), Gilbert
patent: 5035893 (1991-07-01), Shioya et al.
patent: 5384125 (1995-01-01), DiPippo et al.
An Haak Karl W.
Kaessmann Hans-J urgen
An Haak Karl W.
Cho David J.
Dubno Herbert
Isabella David
Myers Jonathan
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