WO2000009176A1

WO2000009176A1 - A wound treatment composition and a wound dressing containing it

Info

Publication number: WO2000009176A1
Application number: PCT/ZA1999/000062
Authority: WO
Inventors: Susanna Elizabeth Chalmers
Original assignee: Susanna Elizabeth Chalmers
Priority date: 1998-08-11
Filing date: 1999-08-11
Publication date: 2000-02-24
Also published as: AU5929499A

Abstract

A wound treatment composition is provided comprising an adsorbent material for adsorbing moisture on or around a wound; and, a saccharide or polysaccharide or derivative thereof. The composition is preferably carried within an envelope in the form of a dressing, conveniently a sachet, with at least a part of the envelope being of a moisture permeable material. A preferred composition includes sucrose and silica gel.

Description

A WOUND TREATMENT COMPOSITION AND A WOUND DRESSING

CONTAINING IT

FIELD OF THE INVENTION

This invention relates to a wound treatment composition and a wound dressing containing it. More particularly, to invention relates to a composition and wound dressing of the general type described in my earlier South African Patent No 93/9117 and its European counterpart namely European Patent application number 93309828.7, namely, a wound treatment composition and wound dressing which can be used to encourage the more rapid healing of wounds and, in. particular, but not exclusively, relatively large wounds and areas of skin and other exposed areas.

BACKGROUND TO THE INVENTION

In my said earlier South African Patent I describe a wound treatment composition and dressing containing it which is composed of two basic ingredients, namely, and anti-septic or antimicrobial agent and a desiccant by which turned is meant a compound operating on the basis of adsorption rather than one of absorption. The preferred composition is composed of sodium chloride which acts as the antimicrobial agent, and silica gel which acts as the desiccant.

Whilst this composition operatesd highly effectively from a medical and thus healing point of view it has certain disadvantages from the patients' point of view. These are that the sodium chloride tends to migrate through the moisture permeable membrane which generally forms part of the envelope containing the composition, but which in any event forms a barrier between the composition and the wound itself The consequence of this is that the patient suffers considerable pain in consequence of sodium chloride entering the wound There also appeared to be a tendency for the composition to stick to the wound to some extent thereby causing difficulties in removal of the composition or at least the dressing and thus the possibility of further pain to the patient In my attempting to over come this problem I unexpectedly developed an improved composition

OBJECT OF THE INVENTION

It is accordingly an object of this invention to provide a wound treatment composition and dressing containing it which retains, and may even improve the efficacy of the composition and wound dressing described in my said earlier Patent but which diminishes, at least to some extent, the disadvantages identified above

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention there is provided a wound treatment composition comprising

(a) an adsorbent material for adsorbing moisture on or around a wound, and,

(b) a saccharide or polysaccharide or derivative thereof

The adsorbent material is preferably a hyperosmotic agent, such as silica gel or anhydrous calcium chloride The ingredient identified as (b) above preferably contains a polysaccharide which is conveniently sucrose crystals. Numerous other types of saccharide and polysaccharide compounds or derivatives thereof may be used in the alternative including compositions containing same such as, for example, naturally occurring products such as honey.

In addition to the two basic ingredients of the wound treatment composition it may also include and anti-septic or antimicrobial agent such as, for example, inorganic salts which are exemplified by sodium chloride, ammonium chloride, magnesium sulphate, and silver oxide. Iodine and antibiotics are also within the scope of the invention which thus includes sulphonamide antibiotics, penicillins, or tetracyclines. .

The wound treatment composition may also contain an indicator which changes in a visible physical characteristic, in particular its colour, in the presence of moisture to indicate moisture saturation of the wound treatment composition and, accordingly, the necessity for changing it. The indicator may be cobaltous chloride (CoCI₂) which is blue in its anhydrous form, but which turns pink when hydrated. The cobaltous chloride is typically present in an amount of about 0.5% by weight of the wound treatment composition.

The wound treatment composition may be contained within a carrier having a moisture-permeable membrane for application to the wound. The carrier could be an envelope containing the wound treatment composition and being made entirely of a moisture permeable material. The moisture permeable material is preferably a non-woven cellulosic material.

In accordance with another aspect of the invention there is provided a wound dressing comprising a wound treatment composition as defined above contained within an envelope of material having at least one surface which comprises a moisture permeable material.

Preferably, the entire envelope of material comprises a moisture permeable material which may be a non-woven cellulosic material and may be transparent or translucent.

The envelope of material may be a sealed sachet which is substantially flat or may be in the form of a plug, which may be an elongate plug for insertion into the wound.

In the case of a plug, the wound dressing may comprise a holding formation optionally in the form of a tab extending from one end of the plug and optionally formed integrally with the envelope.

The wound dressing may have a moisture impermeable adhesive covering attached thereto.

According to another aspect of the invention there is provided use of a wound treatment composition or wound dressing of the invention in a method of treating an abnormal skin condition of an animal.

The abnormal skin condition may be the result of an insect or animal bite, such as a snake bite; a necrotic condition, such as gangrene and gangrous bed sores, any wound where oedema and/or inflammation exists, including first, second and third degree burns, diabetic ulcers, atherosclerotic and various statis ulcers, blisters, boils, acne, surgical wounds and pressure sores. According to another aspect of the invention a wound treatment kit comprises a wound dressing of the invention; and separate attachment means for maintaining the wound dressing in contact with the wound. In order that the invention may be more fully understood, the implementation thereof will now be further described and exemplified with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is a schematic perspective view of a wound dressing of the invention in the form of a moisture permeable sealed sachet containing a wound treatment composition of the invention in a protective wrapping;

Figure 2 is a sectional view through the wound dressing illustrated in Fifure 1 and taken along line II to II;

Figure 3 is a schematic perspective view of a wound dressing of the invention in the form of four separate sachets of the type illustrated in Figure 1 adhered to a support layer;

Figure 4 is a sectional view through the wound dressing illustrated in Figure 3 and taken along line IV to IV;

Figure 5 is a schematic perspective view of a wound dressing of the invention in the form of an elongate plug in a protective wrapping; Figure 6 is a sectional side view through the wound dressing illustrated in Figure 5 and taken along line VI to VI;

Figure 7 is a schematic perspective view of a wound dressing of the invention in the form of an elongate plug containing an integral tab; and,

Figure 8 is an exploded view of a wound dressing of the type illustrated in Figure 1 and attachable to a wound by means of an adhesive moisture impermeable cover.

DETAILED DESCRIPTION OF THE INVENTION

A wound treatment composition and a wound dressing containing the wound treatment composition according to the invention will now be described. The wound treatment composition and the wound dressing containing it are used primarily to treat abnormal skin conditions in humans and animals. The abnormal skin condition may be the result of an injury to the skin, such as an insect or animal bite, particularly a snake bite, and typically a puffadder bite; necrosis of surrounding tissue, such as gangrene and gangrous bed sores; traumatic wounds to the skin; and any other wound where oedema and/or inflammation exists. The abnormal skin condition may also be a first, second or third degree burn, a diabetic ulcer, atherosclerotic and various stasis ulcers, blisters, boils, acne, surgical wounds and pressure sores.

The wound treatment composition contains an adsorbent material, which is typically silica gel or anhydrous calcium chloride, in a dry particulate form. The adsorbent material adsorbs discharged or exudated fluid from the wound, such as serum and blood, and removes it from the wound surface. It also uplifts oedema. The adsorbent material retains the adsorbed moisture because it is an adsorbent not an absorbent. An absorbent material on the other hand could release moisture back onto the wound once its absorbative capacity had been reached. Silica gel, particularly, is able to adsorb large amounts of moisture, which can only be removed from the silica by heating it to approximately 100'C.

In this regard, the wound dressings of the present invention have an advantage over other conventional wound dressings, such as hyd ocolloidal gels, which absorb moisture physically. This means that with these conventional dressings a point is reached where the gel is saturated and where the more moisture that is absorbed, the more moisture returns to the wound from the gel. This generates a moist environment around the wound which retards wound healing and could promote bacterial growth on the surface of the wound.

The wound treatment composition contains, as provided bt this invention, a saccharide or polysaccharide, which is typically and conveniently, sucrose (sugar), in a particulate form. The polysaccharide, it has been found, forms a syrupy composition within the wound dressing when it is exposed to moisture. This assists in preventing a wound dressing containing a wound treatment composition of the invention from adhering to the surface of the wound. It has also been found, unexpectedly, that it promotes desloughing of the superficial layers of the wound, which promotes healing. Although sucrose itself is an antibacterial composition and has been found to destroy the baeterium C L Welehii, an organism that destroys glucose in a wound, it is considered essential that the sugar itself be bacteria free. It has also been found that the sugar prevents the generation of carbon dioxide and hydrogen gasses in and around the wound which could otherwise be formed by organisms such as C L Welehii. Sugar is also an absorbent material which acts in conjunction with the adsorbent material to remove moisture from the surface of a wound quickly.

Although the adsorbent material, typically silica gel, itself has antibacterial properties in that it acts as a hyperosmotic agent, the properties of which are discussed more fully below, the wound dressing composition of the invention may also contain a further antiseptic or antimicrobial agent. The antiseptic or anti-microbial agent may be of the type which acts directly on the bacteria, such as an antibiotic or anti-fungal agent, , or may be another hyperosmotic agent. A hyperosmotic agent causes the cell walls of the bacteria and other disease-causing microorganisms to be lysed.

The antiseptic or antimicrobial agents, which include anti-fungal agents, are usually selected from an inorganic salt, such as sodium chloride, ammonium chloride, magnesium sulphate or silver oxide, or may be iodine, typically iodine crystals, or may be an antibiotic, typically a sulphonamide antibiotic, penicillin or a tetracycline. All these are capable of inhibiting growth and multiplication and killing bacteria and other disease-causing microorganisms on the wound surface. Although organic antimicrobials and antiseptics are included within the scope of the invention, it has been found that such substances may cause allergies in patients sensitive to these chemicals, and are also relatively costly.

The moisture or exudate taken up by the wound treatment composition will typically contain millions of bacterial cells and other disease-causing microorganism cells, and it is therefore essential that such bacteria or other disease causing microorganisms be destroyed so that they cannot re-infect the wound. The antiseptic or antimicrobial agent has a dual function. It both discourages the growth of bacteria and other disease- causing microorganisms on the surface of the wound and it discourages the growth of bacteria and other disease-causing microorganisms in the wound treatment composition itself.

The wound treatment composition of the invention may contain an indicator. An indicator such as cobaltous chloride typically has a blue colour in its anhydrous form, indicating that the wound treatment composition is capable of adsorbing more moisture. Once the wound treatment composition is saturated, however, the indicator becomes fully hydrated and changes colour to pink. This indicates that the wound dressing must be changed. A detection device, detectable by means of X- ray detection, may also be incorporated in a dressing of the invention so that a wound dressing of the invention can be detected easily in a wound, typically before, during and after surgery.

The wound treatment composition of the invention is typically contained in a carrier, which may be an envelope or sachet of differing sizes depending on the size of the wound to be treated. In the case of a sachet it may be made out of a liquid permeable material which is heat sealed along its edges. In any event, a permeable surface of the envelope is usually placed against the wound, although in certain cases a thin layer of gauze may be placed directly against the wound and the wound dressing may then be placed on the gauze.

The moisture and exudate, including any bacteria and other disease- causing microorganisms, pass from the wound through the permeable walls of the envelope of the wound dressings of the invention. The adsorbent adsorbs the moisture so that it cannot pass back through the walls of the envelope onto the wound. Thus, the actual wound treatment composition of the invention does not come into direct physical contact with the skin. This obviates any possible skin irritation problems which may occur with direct contact between the skin and the antiseptic and/or antimicrobial agents within the wound treatment composition. Further, the inhibited and/or killed bacteria and other disease causing microorganisms are kept within the walls of the envelope and do not come into physical contact with the skin again.

In one embodiment of the invention the envelope is a sachet 10, as shown in Figure 1 , which is heat sealed along its edges and which is made of a moisture permeable, non-woven cellulosic material such as a material which is currently marketed under the trademark LUTRISAL^®. The dry particulate wound treatment composition 12 of the invention is contained within the sachet 10 as shown in Figure 1. As also shown in Figure 1 , the wound dressings of the invention are contained within a protective sealed outer wrapping 14 and are steπlized after they are wrapped, for example by gamma irradiation.

A plurality of sachets 10 of the type illustrated in Figure 1 may be adhered to a support layer 16, as shown in Figure 3. The support layer 16 may also be made of a non-woven material and has a plastics moisture impermeable backing layer 18. The plastics material may be polyethylene.

This moisture impermeable backing layer 18 is important in that it isolates the sachets 10 from the surrounding atmosphere, which contains a certain amount of moisture, and thus prevents this moisture from adsorbing to the silica gel or other adsorbent material within the sachets The entire dressing is then surrounded by an envelope 20 of thin moisture permeable material This wound dressing 11 would typically be used for larger wounds The wound dressing 11 may be retained on the surface of the wound by applying an adhesive tape to it or a crepe bandage around it

The wound dressing illustrated in any one of Figures 1 to 4 may also have a water impermeable adhesive cover (not shown) overlying it to adhere it to the wound The adhesive covering may have adhesive strips extending beyond its edges

Figure 8 shows how a sachet of the invention, with no adhesive covering attached directly to it, is applied to the surface of the wound and held in position by applying a separate, adhesive moisture impermeable covering 22 over it A backing layer, which protects the adhesive of the adhesive cover is peeled away prior to placing it over the sachet 10

The wound dressings of the invention may also be in the form of an elongate plug 30 or 32, as shown in Figures 5 and 6 or Figure 7 The envelope of material 26 surrounding the wound treatment composition 12 in a plug is made from the same or a similar moisture permeable material to that of the sachet 10 The plug is packed tightly with the wound treatment composition so that it substantially fills the envelope 26, as shown in Figure 6

The plug 32, shown in Figure 7, has an integral tab 34 formed from an extension of the envelope 26 to assist with the insertion and withdrawal of the plug from deep wounds A plug-type wound dressing is ideally suited for deep wounds, such as a wound in a spinal cavity, a wound in a sinus cavity or other bodily cavity. The plug acts as a drain withdrawing exudated fluid, including serum and blood, from the wound and keeps the internal surfaces of the wound clear of debris so that they may heal. An adhesive moisture impermeable covering, for example the covering 22 shown in Figure 7, may be placed over the wound containing a plug of the invention to keep the plug in place and to keep the wound closed if necessary.

As indicated above the wound treatment composition and dressings of this invention avoid the problem of pain to the patient for which the sodium chloride was responsible, and greatly assists tin the removal of the dressings as a result of the layer formed by the polysaccharide which is typically sugar.

The wound dressings of the invention have also been found to have the following advantages:

no advance cleaning of the wound is necessary which means that any granulation taking place is not disturbed;

it is easy and quick to change the dressings of the invention; the wound treatment composition is hypo-allergenic;

the presence of the indicator indicates when a dressing should be changed;

the wound treatment composition produces pain-free debridement of wounds because it is so absorbative; necrotic tissue disintegrates and is adsorbed irreversibly and retained by the wound treatment composition;

the presence of antiseptic or antimicrobial agents in the wound treatment composition prevents the growth of bacteria and other disease-containing organisms inside the wound dressing itself;

bacterial growth is brought under control quickly to allow the wound to heal quickly and naturally;

the dressings are inexpensive; wounds are protected from external penetration of bacteria; and,

odours emitted from the wound are contained.

The wound dressings of the invention may be packaged in a kit form for out-patient use. Such a kit may contain any dressing of the invention. The components of the kit are typically placed in a moisture proof polymeric plastics bag to maintain dryness and sterility of the wound dressing and wound treatment composition. If the dressing is in the form of a sachet as illustrated in Figure 1 , a separate attachment means for maintaining the wound dressing in contact with the wound will also need to be provided as a part of the kit.

A typical composition of the invention contains approximately 4 parts of silica gel to one part of polysaccharide, for example approximately 20g of silica gel and approximately 5g of polysaccharide.

Typically, a wound dressing of the invention is replaced at regular intervals, for example every 4 to 6 hours, depending on the state of the wound.

Analysis of a wound dressing of the invention has provided the following:

Absorbative capacity (DIN 20) 13.3%

Absorbative capacity (DIN 40) 23.1 %

Friability and dust (%) 0. 1 %

Loss at 145'C 0.2%

0.7 mm (Dry Sieve) 0. 32%

+ 1.4 mm (Dry Sieve) 1.3%

pH (aqueous extract) 3.8

It will be understood that numerous variations and permutations of wound treatment composition and dressing are possible within the scope of the invention without departing from the scope hereof which is defined in the following claims.

Claims

CLAIMS:

1. A wound treatment composition comprising: (a) an adsorbent material for adsorbing moisture on or around a wound; and, (b) a saccharide or polysaccharide or derivative thereof.

2. A wound treatment composition as claimed in claim 1 in which the adsorbent material is silica gel or anhydrous calcium chloride.

3. A wound treatment composition as claimed in either of claims 1 or 2 in which ingredient (b) includes a polysaccharide.

4. A wound treatment composition as claimed in any one of the preceding claims in which the polysaccharide is sucrose crystals.

5. A wound treatment composition as claimed in any one of the preceding claims in which ingredient (b) is contained in honey.

6. A wound treatment composition as claimed in any one of the preceding claims in which there is included an anti-septic or antimicrobial agent

7. A wound treatment composition as claimed in claim 6 in which said agent is an inorganic salt.

8. A wound treatment composition as claimed in claim 7 in which the inorganic salt is selected from the group of sodium chloride, ammonium chloride, magnesium sulphate, and silver oxide.

. A wound treatment composition as claimed in any one of claims 6 to 8 in which there is included one or more of iodine, sulphonamide antibiotics, penicillins, and tetracyclines.

10. A wound treatment composition as claimed in any one of the preceding claims in which there is included an indicator which changes in a visible physical characteristic in the presence of moisture to indicate moisture saturation of the wound treatment composition.

11. A wound treatment composition as claimed in claim 10 in which the indicator is cobaltous chloride.

12. A wound treatment composition as claimed in any one of the preceding claims in which the composition is contained within a carrier having a moisture permeable membrane for application to a wound.

13. A wound treatment composition as claimed in claim 12 in which the envelope is made entirely of a moisture permeable material.

14. A wound treatment composition as claimed in either of claims 12 or 13 in which the moisture permeable material is of a non-woven cellulosic mate╧Çal.

15. A wound dressing comprising a wound treatment composition as claimed in any one of the preceding claims contained within an envelope of material having at least one surface which comprises a moisture permeable material.

16. A wound dressing as claimed in claim 15 in which the entire envelope comprises a moisture permeable material.

17. A wound dressing as claimed in claim 16 in which the moisture permeable material is of a non-woven cellulosic material.

18. A wound dressing as claimed in claim any one of claims 15 to 17 in which the envelope of material is a sealed sachet.

19. A wound dressing as claimed in claim any one of claims 15 to 18 in which a holding formation in the form of a tab is formed integrally with the envelope.

20. A wound dressing as claimed in claim any one of claims 15 to 19 in which the wound dressing has a moisture impermeable adhesive covering attached thereto.

21 . The use of a wound treatment composition or wound dressing as claimed in any one of the preceding claims in a method of treating an abnormal skin condition of an animal or human.

22. A wound treatment kit comprising a wound dressing as claimed in any one of claims 15 to 20 and separate attachment means for maintaining the wound dressing in contact with a wound.