CA1323268C

CA1323268C - Wound dressing, its preparation and use

Info

Publication number: CA1323268C
Application number: CA000544571A
Authority: CA
Inventors: Patrick Lewis Blott
Original assignee: Smith and Nephew PLC
Current assignee: Smith and Nephew PLC
Priority date: 1986-08-20
Filing date: 1987-08-14
Publication date: 1993-10-19
Anticipated expiration: 2010-10-19
Also published as: EP0256893A3; JPS6351865A; GB2194446B; AU601471B2; ZA876101B; IE872175L; GB2194446A; DE3789998T2; ES2054680T3; GB8620227D0; GB8719632D0; IE61186B1; AU7719087A; JP2513712B2; DE3789998D1; EP0256893A2; ATE106710T1; US4990144A; EP0256893B1

Abstract

544,571 A B S T R A C T

Wound Dressing, Its Preparation and Use A non-adherent wound dressing comprising a film which contains depressions over the wound contacting area of the dressing is described.
The depressions contain a viscous pharmaceutical composition which is suitable for topical application to the skin and which preferably contains from 1 to 12.5% by weight of antibacterial agent. In a preferred form of the dressing each depression has an aperture at its apex whereby transmission of wound exudate through the dressing to an absorbent placed on the non-wound contacting surface of the dressing is permitted while at the same time the pharmaceutical composition may release its medicament to the environment of the wound.

Description

3232~8 WOUND DRESSING, ITS PREPARATION AND USE

The present invention relates to low adherency wound dressings which may contain a medicament suitable for topical application to wounds, to their preparation and use.

Dressings which consist of a medicated ointment -impregnated open-work support such as tulle gras have baen used for many years for dressing wounds,see for example United Kingdom Patent No. 1090421 and 1599159.
A disadvantage which is found with this type of dressing is that the healing wound may, despite the presence of an ointment, grow into the tulle gra~ and which .~ '' ' .,,, . ,. . , , ................. : -~ . -, :. ...... , ~ :

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- 2 ~ 2 ~ 8 therefore cannot be removed without retraumatising the wound.

European Patent Application No. 171268 discloses an absorbent dressing comprising a bag formed from a film containing apertured depressions and holding pieces of foam. The construction of the film is such as to prevent re-emergence of any absorbed exudate from the dressing. This advantageous property also retards the release of medicament which may be present within the bag.

I have now found that by using a dressing which employs a film containing depressions in which the depressions are substantially full of a medicated viscous pharmaceutical carrier the above disadvantages lS may be mitigated. It is a feature of the prior art dressings that unimpeded transmission of exudate through the dressing to an absorbent element is permitted. The fact that my dressing satisfactorily transmits exudate is suprising since the progress of exudate would seem to ba impeded by the presence of the riscous carrier which fills the depressions and covers the apertures. The dressings of the present invention further show a low propensity to adhere to the wound and effectively release the medicament from the carrier and , ,; - : -- - - : : , ................. .:- ~ . ., ,. ,.- , - , ; ~ . ~ . . : :
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also may provide a metered dose and a metered release rate of the medicament which is not obtainable when using medicated carriers alone.

A dressing comprising a film containing depressions has the added advantage that different types of pharmaceutically acceptable carriers may be held within the depressions whereby more than one medicament may be released to the skin lO surface. Antibacterial agents are particularly suitable for use in this dressing.

Accordingly the present invention provides a non-adherent dressing comprising a film which contains 15 depressions impressed out of the plane of the ~`ilm over the operative area of the dressing and ~lat land areas between the depressions, wherein at least a portion of the depressions contain one or more apertures, which land area may contact the skin when the dressing is in place and a 20 viscous pharmaceutically acceptable carrier contained within the depressions.

The operative area of the drQssing is that area which covers the wound and the area of skin adjacent to the wound.

However, it is preferred that the dressings of the present invention will contain within the depressions a pharmaceutically acceptable carrier containing medicament.

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~ 4 ~ 8 The medicament present in the pharmaceutically acceptable carrier may be any one of those which may be topically applied to the skin including, steroids, debriding agents, wound healing promoters, local anaesthetics, antibacterial agents, antibiotics and the like. Preferably the medicament will comprise antibacterial agent. Suitable antibacterial agents include iodophors such as polyvinyl pyrrolidone-iodine, chlorhexidine and its salts such as the diacetate, digluconate and dihydrochloride, silver compounds such as silver sulphadiazine or may comprise an admixture of two or more compatible antibacterial agents.

The amount of medicament which is applied topically may be regulated by its concentration in the carrier and by the ~requency and dime~sion3 of the depre~sions which hold the carrier.

The carrier will contain a therapeutically effective amount of medicament. Thus for example in a preferred embodiment the carrier will comprise an ointment containing antibacterial agent at a concentration of, for example, 1 to 12.5% by weight based on the weight of the carrier.

- 5 ~ ~ 3~3~8 In one embodiment the film which contains the depressions is continuous, that is does not contain apertures. Aptly the film maybe then formed from a material which has a moisture vapour transmission rate (MVTR) of greater than 250g/m2/24h at 37C and 100% to 10% relative humidity difference, more suitably greater than 500 g/m2/24h and most suitably greater than 1000g/m2/24h when measured using the Payne Cup Method.
In such dressings the normal perspiration of the skin will evaporate through the film and so avoid causing maceration to the underlying skin.

The depressions containing the apertures may be arranged in a pattern within the borders Or the film comprising the dressing. For example, a square dressing lS of 10cm x 10cm might comprise a central portion Or 5cm x 5cm in which the depressions contain apertures surrounded by a border 2.5cm wide of flat film or o~ a film containing unapertured depressions. Alternatively a strip of apertured depressions may extend across the width of the dressing leaving a flat film or a film containing unapertured depressions on two opposite sides.

The ~ilm used in the dressings of the present invention may be considered to have depressions - 6 _ ~3232~8 impressed out of the plane of the film over the operative area of the dressing. Suitably each depression may contain at least one aperture within its walls, however, it is preferred if each depression has a single aperture which may be formed for example by the removal of the apex of the depression during the manufacturing step.

The use of a film containing apertured depressions is further preferred because it is observed that exudate flows rnore freely to any ab~orbent pad used in conjunction with the dre~sing through the apertures thereby reducing ri9k of trapping exudate beneath the dres~ing. It is also observed that dispersal of the medicated carrier from the depressions i~ al~o facilitated.

However, in a favoured embodiment at least a portion of the depressions may each contain one or more apertures. Here the film may be formed, for example from a film which has a low moisture vapour transmission -~
rate as such films have been observed to have an even lower propensity to adhere to the wound than have the previously mentioned moisture vapour permeable films.

i 3 2 3 2 ~ 8 Thus in a favoured aspect the present invention provides a non-adherent wound dressing comprising a film which contains a pattern of depressions therein over the operative area of the dressing and wherein at least a portion of the depressions each contain one or more apertures and contained within the depressions a viscous pharmaceutically acceptable carrier.

The film containing the depression may be considered to have a thickness defined as the perpendicular distance between the tip of the depression or the aperture and the plane of the film.

Suitably the film will have a thickness as hereinbefore defined of from 0.1 to 3 mm, more suitably 0.75 to 2 mm and preferably 1.0 to 1.5 mm.

When apertures are present then suitably the apertures in the film will have an area equivalent to a circle diameSer 0.25mm to 1.5mm and preferably 0.3 to 1.Omm. The open area of the apertured film will suitably be between lO and 25%.

A contribution to the low adherency shown by the dressings of the present invention is believed to be due to the small land area between the depressions. This :: . : .~ , . .: - . .
! ' - 8 - ~ 3~ 8 land area is the area in the operative area of the dressing which may contact the skin when the dressing is in place. Suitably the land area may comprise 5 to 10 of the surface of the film containing the depressions.

Suitably the number of depressions per sq. c~ may be in the range from 4 to 30 per sq. cm, more suitably will be from 5 to 20 per sq. cm and preferably 6 to i2 per sq. cm.

Suitably the ratio of the land area to the area of the depressions may be in the range 1:20 to i:9.

The land area may also contain apertures. These apertures may be suitably from 0.1 to i.O mm and may facilitate the flow of wound lexudate from a heavily exuding wound or where the ointment is not capable of dissolving or dispensing quickly enough to cope with the evolution of exudate.

The dressings of the present invention may have adhesive coated handles along at least one of their edges for the purpose of adhering the dressing to the skin.
Suitably the dressings have adhesire coated handles on two opposed edges. One advantage of using adhesive coated handles is that during the application of the - . . i - .: : .

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dressing a handle may be adhered to the skin to stabilise the dressing and then a second or other handles may be adhered to the skin so that during wear any tendency for the dressing to move relative to the surface of the wound is reduced. Suitable handles and the material from which they may be made are described in European Patent Application No 161865.

Aptly the dressings of the present invention are sterile and are packaged in bacteria-proof, water-proof pouches until required. The dressings may be sealed into the pouch and sterilised by conventional methods.

Alternatively the components Or the dressing may be made separately in a sterile oondition and assembled under sterile conditions and then sealed into a pre-sterilised bacteria-proof, water-proof pouch.
Suitable pouches include one available as 's b w' View Pack (Trade Mark) and vac~um formed styrene trays with foil or styrene lids.

The pharmaceutically acceptable carrier may be bland that is it may not contain any medicamsnt, for example, it may comprise an emollient cream but preferably the carrier will contain medicament.

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The pharmaceutically acceptable carrier is present in individual depressions within the film. It is therefore possible to employ more than one carrier to carry more than one medicament in a single dressing.
The carriers may be spread in a pattern so that the two carriers are mutually non-overlapping. Alternatively two medicaments could be combined in one carrier. It is also possible to contain one medicament within two different carriers which provided different release rates for the medicament, for example one carrier may give rapid release and one may give sustained release.

A film containing depres:3ions but not apertures may be prepared by placing a strip of the film onto an embossed film of polypropylene having a regular pattern of embossments. The two film~; are pas~ed ln contact between the nip of two rollers under pressure. The rollers comprise a silicone rubber coated roller and a metal roller heated to elevated temperature, for example 80 to 100C, depending upon the nature of the film. The film is retrieved as a ~ilm containing depressions impressed out of the plane of the film. The film may be made from an ethylene-vinyl acetate copolymer-styrene incompatible blend or from moisture vapour permeable material such as a hydrophilic polymer ~or example a hydrophilic polyurethane.

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A film containing apertures in the depressions may be prepared by placing a polymer film on to the embossed surface of a thermoplastic polymeric film. The embossments are suitably arranged in a pattern and are in the form of discrete, raised areas with troughs between them. The embossment may be any shape including square truncated pyramidal,hexagonal, conical or hemispherical. A film of polyethylene is placed over the polymer film urging it against the embossments. The three layered sandwich is then subiected to pressure at elevated temperature, for example 80C for a period of time. The temperature, pressure and time required for the process will depend upon t;he properties of the polymer film but will be sufficient for the film to flow away from the tip of the embossment leaving the tops of the embossments uncovered 90 forming the aperture in the depression in the film. The pressure and heat are discontinued and the polyethylene film is removed. The apertures which are uppermost may be covered by a sheet of polyester film which is then adhered lightly to the film surrounding the apertures by a heated iron. The film containing the apertured depressions and polyester film may then be peeled from the embossed thermoplastic polymeric film. The depressions in the film may then be filled with the medicament in its carrier. The embossments of the thermoplastic film may be pretreated ; "", i, " ,~ , ", :, ~: :

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- 12 - ~32~2~8 with a release compound to facilitate release of the film containing the depressions. In a preferred form -the film has geometrically shaped depressions having approximately circular holes at their apex.

Polymeric material which is suitable for preparing films containing the depressions include thermoplastic elastomeric polymers or polymer blends. A favoured polymeric material is a blend of an ethylene-vinyl acetate copolymer and an incompatible polymer such as a polyolefin and particularly polystyrene. A particularly preferred polymeric material is a blend of ~rom 40 to 90 parts by weight of ethylene-vlnyl acetate copolymer and 60 to 10 parts by weight o~ poly~tyrene and more preferably 60 to 90 parts ethylene-vinyl acetate lS copolymer and 40 to 10 parts polystyrene. If necessary the polymeric material may include fillers or whitenin~
materials such as titanium dioxide.

The ~ilm from which the film containing depressions is formed may suitably have a thickness of from 50~m to 120~m and preferably 75 to 100~m.

In an alternative embodiment of the present invention the apertures in the depressions of the film may be covered by a polypropylene film which may be .. . . ... .. . ..

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vacuum formed onto the apertured film whilst it is still in place on the embossed polypropylene film. The apertured film and the polypropylene film may be peeled away from the polypropylene embossed film. The depressions are filled by the carrier in the method hereinafter described and a release paper placed over the carrier.

The medicament when in the dressings of the present invention may be in the form of a pharmaceutical composition which is suitable for topical treatment of skin or wounds for example treatment of burns, ulcers and other skin lesions exposed to the risk o~ infection.
Suitable ~orm~ of the topical composition of this invention include ointments, gels, oily suspensions, emulsions, lotion9, pastes, powders and the like which are viscous enough to be retained in the depressions in the ~ilm.

Pre~erably the composition will be in the form of an ointment and most preferably as a hydrophilic ointment such as an oil-in-water emulsion. Suitable bases are described in Chapter 87 Ointments:Emulsion Bases in Remingtons Pharmaceutical Sciences, 15th Ed.
1975, pages 1532-34. Other suitable ointment bases include those described in British Patent No. 1240545.

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:' A particularly suitable ointment base is therefore an oil-in-water emulsion containing from 0 to 25% of petrolatum or liquid paraffin, 2 to 20~ of a fatty alcohol, 0 to 12% of an emulsifying agent, up to 10% of non-ionic surfactant and 5 to 25% of a polyhydric alcohol and the balance to lO0~ being deionised or distilled water. Aptly the fatty alcohols are those conventionally used in ointments and are water insoluble. Suitable alcohols include stearyl alcohol, cetyl alcohol, lauryl alcohol and myristyl alcohol.
Suitably the emulsifying agent is a glyceryl fatty acid ester and is preferably glyceryl monostearate. Suitable non-ionic surfactants include the polyoxyethylated sorbitan fatty acid esters and sorbitan fatty acid esters. An emulsifying wax may be used in place of both or part of both of the fatty alcohol and non--ionic surfactant. The polyhydric alcohol acts as a humectant and suitable alcohols include propylene glycol, sorbitol or glycerin or mixtures thereof.

An alternative ointment may contain one or a mixture of polyalkylene glycols for example polyethylene glycol. Suitably the ointment may contain a mixture of a high molecular weight polyethylene gly-col and a low molecular weight polyethylene glycol.

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The compositions used in the present invention may be in the form of an aqueous gel. Suitable gelling agents include polyoxyethylene-polyoxypropylene diol block copolymers, polyacrylic acid lightly cross-linked with triallyl sucrose which has been neutralised using an alkali metal hydroxide, cellulosic derivatives such as carboxymethyl cellulose, hydroxymethyl cellulose, natural gums and the like. A preferred group of gelling agents are the polyoxyethylene-polyoxypropylene diol block copolymers which are commercially available as the Pluronics from BASF-Wyandotte. (Pluronic is a registered trade mark of BASF-Wyandotte).

Suitable gel forming block copolymers of polyoxyethylene-polyoxypropylene will have a rnolecular weight from 4,600 to 13,500 (approximately) and will be present in the gel in an amount ~rom 50% ~or the lower molecular weight copolymers to 20~ for the higher molecular weight copolymers, so that the gel when applied topically is neither too stiff nor too fluid.
Typically the gels are formed by mixing together the copolymer and water to form an aqueous solution at a temperature of2C and adding the medicament and then allowing the solution to gel as it warms to ambient temperature. Suitable Pluronics are those designated as F108, F127 and P105.

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~ 16 _ ~ 2 ~3 8 The composition used in the present invention may also be in the form of a hydrophobic ointment. Suitable hydrophobic ointments are those which are formed from white or yellow soft paraffin or a mixture of such with liquid paraffin. A preferred ointment base comprises a mixture of white soft paraffin and liquid paraffin in a ratio of 5:1 to 1:1. However, in general terms aqueous based systems will be preferred.

The hydrophobic ointment base may also contain non-ionic surfactants such as polyoxyethylated sorbitan fatty aoid esterq and sorbitan fatty acid esters. The presence of non-ionic surfactants increases the miqcibili~y of the ointment with wound fluid and aids release of the medicament. Suitably the non-ionic surfactant will be present in an amount from 0.1 to 0.5%. Preferably the non-ionic surfactant i~ 0.1~ of polyoxyethylene sorbitan triolate and 0.1~ sorbitan monopalmitate.

The pharmaceutically acceptable carrier may be placed in the depressions in the film by spreading it over the film using a doctor blade and removing any excess~ The carrier substantially fills the depressions and the polyester film or vacuum-formed polypropylene film covering the apertures prevents the pharmaceutical : . ,. - i. ., " . . ~ ~ :

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composition passing through the apertures. The other side of the apertured film may then be covered by a piece of paper or film which forms a protector during storage. In use the dressing is removed from the pouch, 5 the protector is removed and the dressing placed with the pharmaceutically acceptable carrier against the skin. The polyester film or polypropylene film covering the apertures is then removed. The dressing may be held in place by conventional bandage means. Aptly an absorbent pad may be placed over the apertures to absorb any exudate which might issue from the wound.

Aptly the dre~sings of the present invention are sterile and are packaged in bacteria-proof, water-proof pouches until required. The flressings may be sealed into the pouch and sterilised by conventional methods.

In a further aspect therefore the present invention ~-comprises a method of treatment which comprises applying to the body of an animal a dressing as hereinbefore described.

Preferred embodiments of dressings of the invention will now be described by way of example only and with reference to the drawings in which .' , ~ ' "''" ' ' ' 18 ~ ~3~2~ :

Figure 1 shows a dressing comprising a continuous film containing depressions within a boarder of flat film.

Figure 2 shows a cross-section through the dressing of Figure 1.

Figure 3 shows a dressing comprising a film containing square pyramidal depressions which are apertured.

Figure 4 9hows a cross-section through a portion of`
the dressing of Figure 3.

Figure 5 shows a dressing comprising a f'ilm containing conical depressions the inner rows which are apertured and the outer rows which are continuous.

Figure 6 shows a cross-section through the dressing of Figure 5.

Figures 7 and 9 show a dressing comprising a continuous film with alternative patterns of depressions. -~

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Figures 8 and 10 show a cross-section through a portion of the dressings shown in Figures 7 and 9 respectively.

Figures 11 and 12 show magnified portions of dressings of the type shown in Figures l and 5 respectively in which the land area between the depressions contains apertures.

The dressing illustrated in Figure 1 shows a dressing (1) formed from a continuous film (2) which ¢ontains a pattern of depressions (3) in the form of a strip which lies in the centre of the dressing (l) and is the operative area of the dressing. The ~ilm is formed from a moisture vapour permeable material such as a polyurethane, for example all Estane (Trade mark), an elastomeric polyester, f`or example a Hytrel (Trade mark) and a polyether-polyamide for example a Pebax (Trade mark). A preferred film may be prepared from a hydrophilic polymer such as a hydrophilic polyurethane which aptly contains from 20 to 40% by weight of water when hydrated. Suitable hydrophilic polyurethanes are described in Vnited Kingdom Patent No 2093190B, The film ~4) which surrounds the depressions (3) is flat and could carry a coating of a skin-compatible - 20 - ~ 3 23 2 ~g pressure sensitive adhesive for ad'nering the dressing to the skin. The pharmaceutically acce?table carrier is contained within the depressions (3).

Figure 2 shows a cross-section through the dressing shown in Figure 1 along the line 2 - 2. The figure shows the relatively small amount of land area (5) between the depressions (3). Only a small amount of this area (5) would contact the skin over the wound and hence the dressing shows low wound adherency. `

Figure 3 shows a ~econd embodiment of a dressing of the present invention. The dressing (6) comprises a film (7) which contains depressions (8) in the form of qquare pyramids the apices of which have been removed during their preparation. I~ this embodiment the ~ilm is completely covered by depressions. The pharmaceutically acceptable carrier (9) may be placed in ;~
any or all of the depressions (8). Prior to use the dressing is sandwiched between two removable -~
protector layers (not shown) to prevent the carrier being ejected from the depressions for example during transportation or storage. The film is suitably formed ;
from a blend of ethylene-vinyl acetate copolymer and polystyrene.

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Figure 4 shows a cross-section through a portion of a dressing shown in Figure 3. The depressions (8) are caused to contain apertures (10) by removing the apices of the square pyramids in the forming process. The pharmaceutically acceptable carrier (9) is placed in the depressions (8). The land area (11) between the depressions (8) forms from 5 to 10% of the area of the film.

Figure 5 shows a third embodiment of a dressing of the present invention. The dressing (12) comprises a `
film (13) which contains a pattern of conical depressions (14). In this dre~sing the two outer rows of the depressions (14) are not apertured while the inner rows contain an aperture (15) formed by remoYal of lS the apices of the cone during manufacture.

Figure 6 shows a cross-section through a dressing shown in Figure 5 along the line 6-6. The outer two rows of depressions (14~ are not apertured while the centre three rows are apertured.

Figures 7 and 9 show dressings ~16, 19) which comprise a continuous film (17, 20~ which has different types of depressions (18, 21) impressed in the film.

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Figures 8 and 10 show the corresponding cross-section views of the dressings 7 and 9.

Figure 11 shows a magnified section of the type of dressing shown in Figure 1 which comprises a dressing (22) formed from a continuous film (23) having depressions (24) impressed out of the plane of the film.
The land areas (25) contain small perforations (26) which permit transmission of wound exudate from heavily exuding wounds.

Figure 12 shows a magnlfied section of the type of dressing shown in Figure 5 whlch compri~es a dressing (2~) formed from a film (28) having conical depressions (29) the outer rows (30) of which are not apertured and the inner rows (31) which are apertured. The land areas lS (32) contain apertures (33) close to the non-apertured depressions (30).
'' Example 1 A film was prepared by extruding a blend of ethylene-vinyl acetate copolymer (80 parts by weight), high impact polystyrene (20 parts by weight) and titanium dioxide (4% by weight of the weight of .,:, ., . ,. .- ; :' :

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polymers). The film had a thickness of 75 to lOO~m. A
strip of the film was placed on an embossed film of polypropylene having hexagonal bosses arranged so that there are 10 embossments per sq.cm. (approx). The two s films were passed in contact between the nip of two rollers under pressure, a silicone rubber coated roller and a metal roller heated to 100C with a silicone rubber mat being in contact with the other side of the blend film. A second pass was made between a silicone rubber roller and a metal roller at 100c to form the apertures, (if a non-apertured film is required this second pass will be omitted), whereby the excess polymer blend material from the apertures is removed on the metal roller. The embossed apertured polymer blend film was then removed from the polypropylene embossed film and then re-applied. A film of polyester was lightly adhered to the blend film over the apertures using pressure and heat. The embossed apertured film -polyester laminate was then recovered from the polypropylene embossed film to provide the laminate of embossed apertured film containg depressions adhered to a polyester film which contacted and covered the apertures of the film.

An ointment comprising 1% silver sulphadia~ine in a hydrophilic ointment was spread over the polymer blend .. ~ ~. . ..

~3~`~2~8 film dressing so that the ointment entered into the depression. Any excess ointment was removed by scraping the surface with a flat blade. The presence of the polyester film prevents the ointment from running out through the apertures. The dressing may be covered by a second releaseable layer and packaged in a bacteria proof, water-proof pack and sterilised by 2.5 Mrad gamma-irradiation.

Example 2 A film was prepared by extruding a blend of ethylene-vinyl acetate copolymer (90 parts by weight), high impact polystyrene (lO parts by weight) and titanium dioxide (4% by weight of the weight of polymers). The film had a thickness Or 80~m. A strip of the film was placed on an embossed film o~
polypropylene having hexagonal embossment arranged so that there are 10 embossments per sq.cm. The two films were passed in contact between the nip of two rollers under pressure, a silicone rubber coated roller and a metal roller heated to 100C. A rigid, plain film of polyethylene was then placed onto the polymer blend film and a second pass was made between the nip o~ two metal rollers heated to 100C. The film sandwich was allowed to cool and the polyethylene film removed. A film of : - . . ; .

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polyester (Melinex, trade mark) was lightly adhered to the embossed film over the apertures using pressure and heat. The embossed polymer blend film was then removed from the polyethylene embossed film, to provide a laminate of embossed polymer blend ~ilm adhered to a polyester film which contacted and covered the apertures of the embossed film.

An ointment was prepared by mixing together polyethylene glycol 400 (70 parts by weight), polyethylene glycol 4000 (20 parts by weight) and polyviny1 pyrrolidone - iodine (10 parts by weight).

The ointment was spread over the polymer blend embossed film dressing so that; the ointment was filled into the depres~ions~ Any exc!ess ointment was removed by scraping the surface with a flat blade. The presence of` the polyester film prevents the ointment ~rom running out through the apertures. The dressing may be covered by a second releasable layer and packaged in a bacteria proof, water-proof pack and sterilised by gamma-irradiation.

In use the dressing is removed from the pack andthe first relea~e layer removed, the dressing is then placed with the ointment against the skin and the . .

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polyester film is removed. An absorbent pad may be placed onto the dressing in contact with the apertures.

Example 3 A polymer blend film was embossed in a similar manner to that described in Example 1. Instead of using a polyester film, a polypropylene film was vacuum formed over the embossed film to cover the apertures. The laminate could be peeled from the polyethylene embossed film because the polymer blend film adhered more strongly to the polypropylene than to the polyethylene.
The ointment was then filled into the depressions as before in Example 1 and the dressing packaged and sterilised as previously.

In use the dressing was placed against the s~in and the vacuum formed polypropylene peeled off.

Example 4 A dressing similar to that described in Example 1 was prepared except that the ointment was formed from an oil-in-water emulsion containing silYer sulphadiazine.

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Example 5 A dressing similar to that described in Example 1 was prepared except that the ointment was formed from an oil-in-water emulsion containing chlorhexidine di gluconate or chlorhexidine diacetate.

Example 6 A film of a thermoplastic polyurethane, Estane 571 4F, is placed against an embossed film of polypropylene. The two films are passed on contact between the nip of two rollers under pressure and at an elevated temperature. Depressions are formed in the polyurethane film without creating apertures. The film i8 removed from the embossmenl;s and an oil-in-water composition containing silver sulphadiazine is filled into the depressions and covered by a removable protector. The dressing so formed may be placed in a vacuum formed styrene tray and covered with a ~oil lid and sterilised.

Example 7 A dressing similar to that described in Example 6 is prepared except that the film used is a - . : : ,:: , . :

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~3232~8 polyetherpolyester elastomer, Hytrel 4056 and the composition comprises 10% polyvinyl pyrrolidone-iodine in a polyethylene glycol carrier~

Example 8 A dressing similar to that describd in Example 6 is prepared using a hydrophilic polyurethane prepared in manner described in Example 2 of United Kingdom Patent No. 2093190B. The depressions are filled with a hydrophobic ointment composition containing chlorhexidine digluconate and a surfactant.

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Claims

1. A non-adherent dressing comprising a film which contains depressions impressed out of the plane of the film over the operative area of the dressing and flat land areas between the depressions, wherein at least a portion of the depressions contain one or more apertures, which land area may contact the skin when the dressing is in place and a viscous pharmaceutically acceptable carrier contained within the depressions.

2. A wound dressing according to claim 1 in which the pharmaceutically acceptable carrier contains a therapeutically effective amount of at least one medicament.

3. A wound dressing according to claim 2 in which the pharmaceutically acceptable carrier contains from 1 to 12.5% of antibacterial agent.

4. A wound dressing according to claim 3 in which the antibacterial agent comprises silver sulphadiazine.

5. A wound dressing according to claim 3 in which the antibacterial agent comprises polyvinyl pyrrolidone-iodine.

6. A wound dressing according to claim 3 in which the antibacterial agent comprises a salt of chlorhexidine.

7. A wound dressing according to claim 1 in which the film which contains the depressions is continuous and has a moisture vapour transmission rate of greater than 250gm-1 24h-1 at 37°C and 100% to 10% relative humidity difference.

8. A wound dressing according to claim 1 in which the film contains a pattern of apertured and continuous depressions.

9. A wound dressing according to claim 1 in which each depression has an aperture at its apex.

10. A wound dressing according to claim 1 in which the apertures have an area equivalent to a circle of diameter 0.25 mm to 1.5 mm and the film has an open area of between 10 and 25%.

11. A wound dressing according to claim 1 in which the land area between the depressions comprises from 5 to 10% of the surface of the film containing the depressions.

12. A wound dressing according to claim 1 in which the film is formed from a blend of ethylene-vinyl acetate copolymer and polystyrene.

13. A wound dressing according to claim 1 in which the viscous pharmaceutically acceptable carrier is an oil-in-water emulsion.

14. A wound dressing according to claim 1 in which the viscous pharmaceutically acceptable carrier is an aqueous gel.

15. A wound dressing according to claim 1 in which the viscous pharmaceutically acceptable carrier is a hydrophobic ointment.

16. A wound dressing according to claim 1 which is sterile and is packaged in a bacteria-proof and waterproof pack.

17. A wound dressing according to claim 1 in which the thickness of the film which contains depressions is from 0.1 to 3 mm.

18. A wound dressing according to claim 1 in which the film contains from 4 to 30 depressions per square centimeter.

19. A wound dressing according to claim 1 in which the ratio of the land area to the area of depressions is 1:20 to 1:9.

20. A wound dressing according to claim 1 in which the land area also contains apertures which may be from 0.1 to 1.0 mm in diameter.

21. A wound dressing according to claim 1 in which the viscous pharmaceutically acceptable carrier is a hydrophilic ointment.

22. A non-adherent wound dressing comprising a film which contains depressions impressed out of the plane of the film over the operative area of the dressing and a viscous pharmaceutically acceptable carrier contained within the depressions wherein at least a portion of the depressions contain one or more apertures, wherein the film carries along at least one edge an adhesive coated handle capable of adhering to the skin.

23. A wound dressing according to claim 22 in which the dressing carries adhesive coated handles along two opposed edges.

24. A non-adherent wound dressing comprising a film which contains depressions impressed out of the plane of the film over the operative area of the dressing and flat land area between the depressions, wherein at least a portion of the depressions contain one or more apertures, which land area may contact the skin when the dressing is in place and a viscous pharmaceutically acceptable carrier containing a therapeutically effective amount of at least one medicament, contained within the depressions, wherein the pharmaceutically acceptable carrier is a hydrophilic ointment, the medicament is polyvinylpyrrolidone-iodine and the film is a blend of ethylene-vinyl acetate copolymer and polystyrene.

25. The use of a dressing comprising a film which contains depressions impressed out of the plane of the film over the operative area of the dressing and a viscous pharmaceutically acceptable carrier contained within the depressions wherein at least a portion of the depressions contain one or more apertures, wherein the film carries along at least one edge an adhesive coated handle capable of adhering to the skin, to treat a wound.

26. The use according to claim 25 in which the viscous pharmaceutically acceptable carrier contains from 1 to 12.5% of antibacterial agent.