Dressings, manufacture and use

A dressing which comprises an ointment impregnated open-work support, having a protector on at least one face thereof characterized in that the protector is a film soluble in water, materials therefor and the manufacture thereof are described.

The present invention relates to dressings suitable for application to 
wounds, materials therefore and the manufacture thereof. 
Dressings consisting of an ointment impregnated open-work support such as 
tulle gras (sometimes called petrolatum gauzes) have been used for many 
years for dressing wounds. A soft paraffin tulle gras is disclosed in 
German Offenlegeschrift No. 2805248. Conventionally tulle gras are 
provided in sterile pouches. The tulle gras are prevented from adhering to 
the walls of the pouch (or to each other if more than one is packed in a 
pouch) by sheets of paper. When the gras is removed from the pouch the 
sheets of paper are pulled from the petrolatum and the gras placed on the 
wound. Occasionally this procedure results in the loss of petrolatum and 
if the gras is medicated then loss of medicament can also occur. Clearly 
it would be desirable to be able to avoid the use of paper or like 
material to protect the gras and like ointment impregnated open-work 
support dressings. It has now been discovered that soluble films may be 
employed that obviate the need to remove the protector. 
Accordingly the present invention provides a dressing which comprises an 
ointment impregnated open-work support having a protector on at least one 
face thereof, characterised in that the protector is a film soluble in 
water. 
Suitable ointment impregnated open work supports can include any of those 
conventionally used in impregnated gauze dressings of the art. Such 
dressings can employ a hydrophobic or non-water containing hydrophilic 
ointment. 
Preferred ointment impregnated open-work supports are known as tulle gras 
as hereinbefore mentioned. Suitably the tulle gras dressing of the 
invention can comprise a gauze for example a leno gauze impregnated with a 
petroleum based ointment. Normally the petroleum based ointment will be a 
white or yellow petroleum jelly of a pharmaceutical grade optionally 
containing other ingredients for example a surfactant. Petroleum based 
ointments consisting of mixtures of soft paraffin and wool fat are also 
suitable. 
Preferably the dressing is a sterile dressing. Aptly the sterile dressing 
is within a bacteria-proof pack, for example, a pouch. Suitable packs and 
sterilising procedures are described hereinafter. 
In another aspect the invention provides a sterile dressing which comprises 
a tulle gras, a protector on at least one face of the tulle gras and a 
pouch enclosing the tulle gras and protector; characterised in that the 
protector is a film soluble in water. 
For use the pouch may be opened and the tulle gras with protector removed 
and placed on the wound. The protector can then dissolve in the fluid 
released from the wound and its environment and the tulle gras is then 
free to fulfill its conventional function. 
Most aptly both faces of the tulle gras are provided with a protector in 
the form of film soluble in water. 
The film may be composed of any pharmaceutically acceptable water soluble 
material such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, 
hydroxypropylcellulose, sodium carboxymethylcellulose, polyvinyl 
pyrrolidone, alginates and the like or mixtures thereof. 
Most suitably the film is composed of polyvinyl alcohol. When used herein 
the term polyvinyl alcohol includes polyvinyl alcohol and partially 
acetylated polyvinyl alcohol. Most favourably this film is composed of 
polyvinyl alcohol in which 10% to 33% of the hydroxyl groups are 
acetylated, preferably 15% to 25% of the hydroxyl groups are acetylated 
and 10% to 22% of the hydroxyl groups are acetylated. 
Aptly the polyvinyl alcohol employed in this invention has a molecular 
weight of from 15,000 to 120,000 more suitably from 20,000 to 100,000 and 
preferably from 25,000 to 85,000. 
A favoured polyvinyl alcohol is Gohsenol GLO5 made by Nippon Gohsei and 
available from British Traders and Shippers Limited. Gohsenol GLO5 has a 
molecular weight of 30,000 and a degree of hydrolysis of 87% to 89%. 
The water soluble film will generally contain from 1 to 50% of plasticizer, 
more usually from 5 to 40% of plasticizer, favourably from 8 to 30% of 
plasticizer and preferably from 10 to 25% of plasticizer. 
The plasticizer employed in the film will normally be water, an alcohol or 
mixture thereof. Frequently the film will contain up to 25% water, more 
usually 1 to 20% water and commonly 2 to 10% water. The alcohol employed 
will usually be a di- or trihydroxylic compound such as ethylene glycol, 
propylene glycol, tetramethylene glycol, glycerol or the like. Favoured 
alcohols include propylene glycol and glycerol of which glycerol is 
normally preferred. Frequently the film will contain 1 to 25% of the 
alcohol, more usually 1 to 20% of the alcohol and favourably 8 to 15% of 
the alcohol. 
Suitable water soluble films for use as a protector on dressings of the 
invention can have a weight per unit area of 10 to 125 g/m.sup.2 and 
preferably a weight per unit area of 15 to 50 g/m.sup.2. The water soluble 
film can be a film of substantially uniform thickness or a film of thinner 
areas. Suitably such films can have a thickness of 10 to 125 microns and 
preferably a thickness of 12.5 to 50 microns. 
A favoured water soluble film is a polyvinyl alcohol (Gohsenol GLO5) film 
of approximately 25 micron thickness containing 5 to 15% by weight of a 
glycerol plasticizer. 
Advantageously the water soluble film can have thinner areas to aid 
dispersal of the film in water. Such thinner areas are preferably in the 
form of recesses arranged in a uniform pattern on one or both surfaces of 
the film. Suitable recesses include grooves, which may be interconnected, 
for example intersecting sets of straight parallel grooves and 
depressions, which may be discrete, of for example triangular, 
rectangular, circular or a like geometric shape. 
An apt water soluble film having thinner areas is a polyvinyl alcohol film 
which is known as Hi-Selon C type film manufactured by Nippon Gohsei and 
supplied by British Traders and Shippers Limited. Hi-Selon C type film is 
an embossed film of a water soluble polyvinyl alcohol with a degree of 
hydrolysis of 87% to 89% and a molecular weight of 44,000 to 72,000. The 
film is plasticized with a humectant type plasticizer such as polyethylene 
glycol and has an equilibrium moisture content of 8% to 10% at 20.degree. 
C. and 65% relative humidity. Hi-Selon C type film has an embossed pattern 
of approximately 16 per cm parallel straight grooves in both the 
longitudinal and transverse directions which intersect at an angle of 
90.degree. to form a square grid pattern. 
Favoured water soluble film having thinner areas are polyvinyl alcohol 
(Gohsenol GLO5) films of weight per unit area of 20 to 50 g/m.sup.2 
containing 5 to 15% by weight of glycerol with a uniform pattern of 
triangular shaped depressions on one surface. 
The ointment of a dressing of the invention can optionally contain a 
medicament. Suitable medicaments include silver sulphadiazine, 
chlorhexidine acetate and povidone iodine. 
The medicament employed is normally a curative agent which is topically 
effective. One particular class of curative agents envisaged for use in 
this invention is the topically applicable anti-infective agents. Such 
agents include chlorhexidine salts such as the gluconate, acetate, 
hydrochloride or the like; silver salts such as silver sulphadiazine; 
iodophors such as polyvinyl-pyrrolidone-iodone or the like; benzalkonium 
chloride or other topically acceptable antibacterial agent. Such agents 
also include fucidic acid salts such as the sodium salt; neomycin salts 
such as the sulphate or hydrochloride and other topically acceptable 
antibiotics. 
It is preferred that the medicament is a powder. Suitable powders have a 
mean particle size of 1 micron to 500 microns and preferably have a mean 
particle size of 2 microns to 300 microns for example 5 microns to 250 
microns. 
Favoured povidone iodine powders are grades 30/06 and 17/12 manufactured by 
B.A.S.F. and presently available from Blagden Chemicals Limited. 
Grade 30/06 has a mean particle size of 200 microns, average molecular 
weight of 40,000 and available I.sub.2 content of 9% to 12%. 
Grade 17/12 has a particle size of less than 150 microns, an average 
molecular weight of about 10,000 and an available I.sub.1 content of 9% to 
12%. 
Povidone-Iodine powders of these grades with average particle sizes as low 
as 10 microns are also suitable. 
A favoured chlorhexidine acetate powder has a mean particle size of 10 
microns. 
A favoured silver sulphadiazine powder has a mean particle size of 2 
microns to 5 microns. 
Normally the medicament will be present as 0.1% to 25% by weight of the 
ointment and usually as 0.4% to 15% by weight of the ointment. 
In another aspect the invention provides a process of making a dressing of 
the invention which comprises placing a film soluble in water on one or 
both sides of an ointment impregnated open work support. 
The ointment impregnated mesh fabric can be prepared in a conventional 
manner. 
In a continuous process it is convenient to laminate a film soluble in 
water to one or both sides of an ointment impregnated open work support to 
form a continuous strip and to cut the strip into dressings of suitable 
size. 
The sterile dressings of this invention may be prepared by placing a film 
soluble in water on one or both sides of the ointment impregnated 
open-work support for example a tulle gras, sealing the dressing into a 
bacteria proof pack such as a pouch and sterilizing the pouch and its 
contents. 
Suitable water soluble polymer films can be made by hot melt extrusion or 
by casting the polymer onto a release surface or the like. Polyvinyl 
alcohol films can be conveniently made by casting a 4% to 35% by weight 
aqueous solution of the polymer in a conventional manner for example by 
means of a doctor blade over flat bed coating head onto a polyethylene 
coated paper and then drying in an oven at 85.degree. C. A favoured 
polyethylene coated paper is known as Steralese 15 made by Sterling Coated 
Papers Limited. 
Suitable water soluble films having thinner areas can be made by casting 
the polymer, as a solution or a hot melt, in contact with a surface having 
a pattern of raised areas. These films can also be made by embossing a 
film with a similar patterned surface. 
An apt process of forming such films comprises casting an aqueous solution 
of polymer in contact with a sheet embossed with uniform pattern of raised 
areas. 
A favoured process of forming a polyvinyl alcohol film with thinner areas 
comprises casting an aqueous solution of polyvinyl alcohol (30% by weight 
of Gohsenol GLO5) containing a plasticizer (5% to 15% by weight of 
glycerol) by means of a doctor blade over flat bed coating head onto a 
sheet embossed with a uniform pattern of raised triangles (polyethylene 
film type 04514 emboss code 14 available from AOE Plastics GmbH). 
The pouches employed are most aptly made of paper or some other ethylene 
oxide permeable material as a favoured method of sterilization is by 
treatment with ethylene oxide in conventional manner. Alternatively the 
pouches can be made of a heat sealable aluminium foil laminate. Suitable 
heat sealable aluminium foil laminates for example a paper/aluminium 
foil/ethylene vinyl acetate/lacquer laminate are available from DRG 
Flexible Packaging Limited. Suitable sterilization methods for aluminium 
foil laminate pouches include gamma irradiation. 
The use of a water soluble film protector on dressings of the invention 
which does not require removal avoids the loss of ointment incurred when a 
protector is removed from conventional dressing. This allows the open work 
support of dressings of the invention to be impregnated with a lower 
weight per unit area of ointment than that of conventional dressings 
(typically 250 g/m.sup.2) without loss of dressing efficiency. 
Suitably the open work support of dressings of the invention can be 
impregnated with a weight per unit area of 100 to 220 g/m.sup.2 and 
preferably a weight per unit area of 120 to 200 g/m.sup.2.

The following Examples illustrate the invention: 
EXAMPLE 1 
A 10 cm wide strip of Leno gauze impregnated with petroleum jelly was laid 
onto a 10 cm wide length of 20 microns thick polyvinyl alcohol film 
(Hi-Selon C type embossed film) and a further 10 cm wide length of 
polyvinyl alcohol film placed on top to form a laminate of impregnated 
gauze between two layers of film. The laminate strip was then cut into 10 
cm.times.10 cm dressings which were packed individually into sealed 
aluminium foil pouches and sterilized by gamma irradiation (2.5 megarads) 
in a conventional manner. 
EXAMPLE 2 
In a similar manner to example 1 a medicated tulle gras dressing of the 
invention was made by impregnating a Leno gauze with 150 to 200 g/m.sup.2 
of petroleum jelly B.P. containing 0.525% by weight of chlorhexidine 
acetate (micronised powder from ICI Pharmaceuticals Limited). 
EXAMPLE 3 
A 10 cm wide strip of Leno gauze impregnated with petroleum jelly B.P. (160 
g/m.sup.2) containing a surfactant (0.1% by weight of Tween 60) and 
povidone iodine powder (6% by weight of grade 30/06 available from Blagden 
Chemicals Limited) was laid onto a 10 cm wide strip of embossed polyvinyl 
alcohol film (24 gsm) and a similar strip of embossed polyvinyl alcohol 
film placed on top of the impregnated layer to form a laminate. 
The embossed polyvinyl alcohol film was made by coating an aqueous solution 
(30% by weight) of Gohsenol GLO5 containing glycerol (5% by weight) onto 
an embossed polyethylene film (Grade 04514, emboss code 14 available from 
AOE Plastics GmbH) by means of blade over flat bed coating head and drying 
the cast film in an oven at 70.degree. to 80.degree. C. 
The laminate strip was then cut into 10 cm.times.10 cm dressings, packed 
individually into sealed aluminium foil pouches and sterilized by gamma 
irradiation (2.5 megarads) in a conventional manner. 
The aluminium foil pouches were formed by edge heat sealing a front foil 
consisting of a bonded paper (40 gsm)/aluminium foil (24 
gsm)/ethylene-vinyl acetate (23 gsm of Surlyn 1652) laminate and a back 
aluminium foil of similar construction coated with heat seal pealable 
lacquer (25 gsm) available from DRG. Flexible Packaging Limited. 
WOUND HEALING STUDIES 
The dressings of Example 3 were placed on partial thickness wounds (2.5 
cm.times.2.5 cm) made on the backs of pigs (large white breed). It was 
found that the water soluble protectors of these dressings, in contact 
with the wound exudate, dissolved within 1.5 minutes. Examination of wound 
sections over a period of three months showed that the healing and 
pathology of the wounds were not substantially different from that of 
comparative test conventional tulle gras dressing (Jelonet made by T. J. 
Smith and Nephew Limited).