Percutaneous anaesthesia

Details Percutaneous anaesthesia Percutaneous anaesthesia

1993-11-12

1996-01-16

Phelan, J. Gabrielle

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Web, sheet or filament bases; compositions of bandages; or...

424449, 514817, A61F 1300

Patent

active

054846030

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/GB92/00518 filed Mar. 20, 1992.
This invention relates to the administration of percutaneous local anaesthetics and more particularly to delivery systems for the topical administration of amethocaine.
In UK Patent Specification No. 1108837, there is proposed a film-forming composition comprising a copolymer of vinyl acetate and crotonic acid having, for example, amethocaine (2-dimethylaminoethyl .rho.-butyl aminobenzoate) intimately dispersed therethrough. Such compositions are intended for use on mucous membranes and are activated by the action of saliva, for example, which dissolves the film-forming polymer and liberates the anaesthetic agent.
Such compositions cannot readily be employed for local percutaneous anaesthesia where it is highly desirable that both the area of the administration site be strictly controlled and the minimum quantities of anaesthetic are used to provide an effective unit dose.
It is desirable that the anaesthetic containing material can be applied readily and retained on the skin at the place of use. It is also highly desirable that the materials be highly conformable.
Although it has been proposed to laminate or cover the local anaesthetic containing polymer film with water insoluble, water resistant or water impermeable backing material there have been no proposals to concentrate the amethocaine at the skin contacting surface of the delivery system. We have found that amethocaine has a tendency to migrate towards and, possibly, into the backing layer. Thus in order to provide effective anaesthetic amounts at the point of use, considerably larger quantities than those required for a unit dose have to be incorporated into the film forming polymer. Thus controlled administration may be difficult to achieve and time taken for effective anaesthesia maybe impossible to determine in advance.
We have now found that effective anaesthesia may be obtained reproducibly and in a minimum amount of time by use of a highly conformable dressing-type applicator system wherein the amethocaine is concentrated and retained in the skin-contacting region of the delivery system.


BRIEF DESCRIPTION OF THE DRAWINGS

The anaesthetic delivery system is more clearly described in the following discussion and drawings in which:
FIG. 1 is a cross section of a dressing in accordance with the present invention;
FIG. 2 is a cross section of the dressing of FIG. 1, provided with an aperture in the skin contacting layer;
FIG. 3 is a cross section of the dressing of FIGS. 1 and 2, without the carrier layer and with a two part self removable protector sheet;
FIG. 4 is a cross section of a dressing of the present invention wherein the intermediate layer is a coverstock layer; and
FIG. 5 is a cross section modification of dressing of FIG. 4, wherein the backing layer is apertured.
In accordance with the present invention there is provided a percutaneous anaesthetic delivery system comprising a skin conformable backing layer, an amethocaine-bearing material and a layer having little or no tendency to absorb amethocaine intermediate the backing layer and the layer of amethocaine bearing material.
The amethocaine-bearing material maybe a water-soluble or water-dispersible film forming material having amethocaine intimately mixed and distributed therethrough. The amethocaine loading in the film-forming material preferably should be as high as possible, aptly at least 10% by weight, more aptly at least 40% by weight of the material. Suitably, it will be at least 50%, and most suitably from 60 to 80% by weight. The amount of amethocaine present in the dressing should, aptly be sufficient to deliver at least 0.3 mg cm.sup.-2 to the skin.
The film forming polymer may be any pharmaceutically acceptable water-soluble material which does not adversely react with or affect the amethocaine. Suitable materials include highly water-soluble polymers such as polyvinylpyrrolidone, carbomers such as those sold under the trade name CARBOPOL, polyvinylpyrrolidone-vinyl acetate copolymers and cellulose de

REFERENCES:
patent: 4562060 (1985-12-01), Broberg
patent: 4899739 (1990-02-01), Konishi
patent: 4904475 (1990-02-01), Gale
patent: 4951657 (1990-08-01), Pfister

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