Surgery: splint – brace – or bandage – Bandage structure – Skin laceration or wound cover
Reexamination Certificate
1998-07-13
2001-01-16
Lee, Kim M. (Department: 3761)
Surgery: splint, brace, or bandage
Bandage structure
Skin laceration or wound cover
C602S041000, C602S042000
Reexamination Certificate
active
06175054
ABSTRACT:
The invention relates to water soluble films and in particular water soluble films used to deliver an active substance co a wound.
It is known to use active substances such as antioxidants, deodorants, perfumes or pharmacologically active substances in hydrocolloid wound dressings. In particular it is known to include actives as optional ingredients in a composition forming the wound and skin contacting layer of a wound dressing Such compositions is described in EP-B-0092999, EP-B-130061 or EP-B-190814. Typically the composition comprises a homogeneous blend of hydrocolloid to absord exudate from the wound and an adhesive such as polyisobutylene to stick the dressing to the surrounding skin. Generally the delivery of the active substance from such a dressing is unpredictable and slow because the active is distributed throughout the adhesive layer and not concentrated at the wound and skin contacting surface.
An alternative wound dressing to a hydrocolloid based dressing is one based on fibres sometimes referred to as super-absorbant fibres. Such fibres are described in WO-A-93/12275 which describes modified cellulose fibres and in PCT/GB/9400102 which describes reprocessed alginate fibres. In general, it is difficult to incorporate active substances into such fibres because of the processes used in their manufacture. For example in WO 93/12275 cellulose based fibres are produced according to a method which includes a step in which the fibres are washed with a solution containing a high proportion of industrial alcohol. The use of such a wash on fibres comprising an active substance may cause inactivity or a reduction in activity of the substance.
We have now found that it is possible to incorporate active substances into water soluble films that can be used as part of or in addition to a wound dressing to deliver active substances to a wound.
Accordingly the invention provides a water soluble film having a thickness of from 0.03 mm to 0.5 mm comprising a water soluble polymer and an active substance. Preferably the film thickness is from 0.01 mm to 0.1 mm.
Because of its thinness such a film may predictably and rapidly release active substance into a wound. Such a film may be incorporated into a wound dressing as a separate layer which contacts the wound.
Accordingly the invention provides a wound dressing comprising a water soluble film said film comprising a water soluble polymer and an active substance.
Such a film may be integrally formed as an outer layer of a dressing so as to allow rapid delivery of an active substance to the wound from the dressing. This has the advantage that the active is not subjected co the processing regime of the fibre.
Water soluble polymers suitable for use in the present invention include sodium carboxymethylcellulose and particularly those sodium carboxymethylcelluloses having a viscosity in the range of 200 to 800 mPas, sodium alginate, hyaluronic acid and in particular the sodium salt, hydroxypropylcellulose, polyvinylalcohol, and hydroxyethylcellulose. Preferably the water soluble polymer is present at a level of from 20% to 99.5%, more preferably 30% to 94.5% and most preferably 60% to 90% by weight of the dry film.
Active substances suitable for use in the present invention include antibiotics such as polymyxin B and zinc bacitracin, antimicrobials such as metronidizole and silver sulphur diazine, broad spectrum antimicrobials such as PVPI and free radical scavengers such as vitamin A and vitamin E. Preferably the active substance is present at a level of from 0.5% to 10%, more preferably 0.5% to 40% and most preferably 0.5% to 5% by weight of the dry film.
Films according to the present invention preferably comprise a plasticiser to increase the flexibility of the film. Examples of plasticisers suitable for use in films of the present invention include propylene glycol. glycerol, depanthanol, sodium lactate, polyethylene glycol and sorbitol. When present the plasticiser is preferably present at a level of from 5% to 80%, more preferably 30% to 60% by weight of the dry film.
Films according to the present invention preferably comprise a deodorising agent for example chlorophyllin or Grillocin™. When present the deodorising agent is preferably present at a level of from 0.5% to 15%, more preferably 1% to 10% by weight of the dry film.
Wound dressings according to the present invention comprising a water soluble film comprising a water soluble polymer and an active substance preferably comprise a substrate made from fibres of cellulose, alginate or hyaluronic acid to which the film is attached or a substrate of hydrocolloid such as that described in EP 92999B co which the film is attached.
The following examples illustrate preferred embodiments of the invention.
REFERENCES:
patent: 5681579 (1997-10-01), Freeman
patent: 5735812 (1998-04-01), Handy
Bristol--Myers Squibb Company
Furman, Jr. Theodore R.
Kilcoyne John M.
Lee Kim M.
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