Transdermal device

Details Transdermal device Transdermal device

1993-04-05

1994-10-04

Phelan, D. Gabrielle

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

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

424449, A61F 1302

Patent

active

053524578

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a method of preparing a device for transdermal delivery of an active ingredient and to transdermal devices prepared by that method.
The administration of drugs through the skin is a concept which is now well established and this route has several advantages over more conventional forms of drug delivery such as injection or oral ingestion. A particular advantage is that transdermal drug delivery devices can provide a sustained and controlled release of the active ingredient over a prolonged period so that the resulting blood levels remain constant. This is in contrast to other forms of administration where surges of the agent occur in the bloodstream immediately after administration and then drop away rapidly until the next dose is given. In the case of oral administration the blood level is further influenced by contents of the intestines and therefore difficult to control. Transdermal administration permits direct access to the bloodstream without first passage through the gastrointestinal tract and liver and also without the inherent problems associated with injection such as risk of infection and need for sterile administration equipment.
Because of the advantage of transdermal administration, in recent years a very large number of devices have been developed and described for the transdermal administration of a variety of pharmaceuticals. The devices are usually in the form of a patch or plaster to be attached to the skin. Early devices such as for example, that described in U.S. Pat. No. 3,598,122 comprised a reservoir containing the active ingredient, either in solid or liquid form. The reservoir walls were composed of a material permeable to that ingredient and it was stuck to the skin by a thin layer of adhesive which was also permeable to the active ingredient. The outer surface of the reservoir was covered with a backing material impermeable to the active ingredient. Such devices were bulky and solvents in which the active agent was dissolved tended to interfere with the ability of the adhesive to stick to the skin.
With improvements in adhesives available it was soon found possible, and indeed preferable, to prepare transdermal devices in which the adhesive layer itself provided the drug reservoir. Thus more modern transdermal devices usually comprise at least an impermeable backing material, a layer of drug-containing adhesive attached to the backing material and a release liner on the other adhesive surface which is removed for application of the device to the skin. Additional membranes are sometimes included within the device to regulate the rate of passage of the active agent from the adhesive to the skin.
Various methods have been used to achieve suitable drug/adhesive mixtures in which the active ingredient is dispersed in the adhesive without affecting the ability of the adhesive to stick to the skin. One of the earliest drugs to be administered by a transdermal device was nitroglycerin which is used in the treatment of angina pectoris and congestive cardiac failure. Nitroglycerin is well absorbed by the skin and therefore particularly amenable to transdermal administration. Conveniently it is a liquid at room temperature and so the approach that has been taken is to absorb it on to a solid such as lactose which is then dispersed in a polymer adhesive. Such devices are described in, for example U.S. Pat. No. 4,776,850, G.B. 2,081,582, and others. One or more other "solvents" are sometimes present in the nitroglycerin adhesive mixtures either as permeation enhancers, or for the purpose of "solvent casting" the mixture onto a backing layer.
Where the active ingredient to be incorporated into a transdermal device is a solid any solvent for the agent must be carefully chosen to be compatible with the adhesive. In WO86/00814 for example the problem is overcome by choosing a single solvent which is both a solvent for the drug and a solvent for the adhesive. However such a method restricts severely the number of different drugs which are compatible with a particular adhe

REFERENCES:
patent: 4031894 (1986-09-01), Urquhart et al.
patent: 4746509 (1988-05-01), Haggiage et al.
patent: 4769028 (1988-09-01), Hoffmann
Patent Abstracts of Japan, vol. 12, No. 333 (C-526), Sep. 8, 1988.
Patent Abstracts of Japan, vol. 12, No. 159 (C-495), May 14, 1988.

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