GB1408925A - Medical pad - Google Patents

Abstract

1408925 Dressings IMPERIAL CHEMICAL INDUSTRIES LTD 11 Jan 1973 [14 Feb 1972] 6692/72 Heading A5R [Also in Division Dl] Pad: A pad for administering a medicament comprises a sheet 3 of material provided with fibres 4 in the form of capillary tubes extending through the sheet 3 and projecting from one face thereof for a distance of 20 to 1000 microns. A dressing incorporating the pad comprises a rigid case 1 of metal or plastics material, closed by the sheet 3 so that the fibres 4 projecting outwardly. A reservoir 5 so defined contains the medicament which may be injected through a plug 6. Straps 7 are used to secure the dressing to the skin. The sheet 3 may be intrinsically permeable or be rendered permeable by piercing it in 5 to 10 places. Pressure may be applied to the medicament from a chamber 8 separated from the reservoir 5 by a flexible membrane 9. The chamber 8 may contain polymer-coated sodium bicarbonate granules which liberate carbon dioxide when an acid is injected through a plug 10. Alternatively, the pressure may be applied using a distendible reservoir filled under pressure, a spring-loaded reservoir or a pressure bandage. In an alternative embodiment, the chamber 8 may be omitted. The reservoir may take various forms. For example, it may be a permeable sachet of a plastics material, a foam, a capsule to be pierced before use, a piece of wadding, or a gel. A diffusion layer may be interposed between the reservoir 5 and the pad 3 to control the rate of release of the medication. The diameter of the fibres is 8 to 100 microns and they make an angle of 45‹ to 90‹ with the sheet 3. The fibres 4 may be composed of glass, carbon, alumina, zirconia, silicon nitride, nylon, polyparabenzamide or stainless steel. The sheet 3 may be made of plastics or metal although several materials are stated to be suitable. As one example, the medicament may be polypeptides. Method of manufacture: Four methods of forming pads are given. In one example glass capillary tubes 15cm long and 40 microns in diameter are placed 0.5 mm apart, in parallel manner, on a glass plate, with their ends retained on two strips of double sided adhesive tape. A film, 0.5 mm to 1 mm thick, incorporating the tubes is formed by brushing the tubes with a solution in acetone of cellulose acetate containing acetyl triethyl citrate as plasticiser and allowing the solvent to evaporate. Several such films are prepared and cut into 2.5 cm squares whose faces are brushed with acetone and laid on top of each other to form a cube wherein the tubes are aligned in the same direction. The cube is cut with a microtome, transverse to the direction of alignment of the tubes to form sheets about 1 to 2mm thick. One face of the sheet is etched away by brushing it alternately with acetone and water until about 100 microns of the tubes are exposed. Air is blown through the pad during the etching process to avoid blockage of the tubes.