Drug administration transdermal

What is transdermal drug administration What are the theoretical advantages of this route of administration What considerations must be taken into account when using this route ... 

In membrane diffusion systems the polymer membrane with a given pore size or pore size distribution controls the diffusion of the active substance from the drug reservoir. Dosage forms with membrane-controlled drug delivery can be coated tablets, coated granules or pellets, or so-called multiparticulate systems on which various coats are applied. One possibility for transdermal drug administration is the transdermal patch controlled with a membrane [4-7,34-39]. 

Membrane-controlled Transdermal Drug Administration Drug administration through the intact skin, transdermal therapy, was realized at the end of the 20th century with the development of transdermal therapeutic systems [22, 59]. Various polymers are necessary for this. 

Transdermal Drug Administration Controlled with Matrix Diffusion Drug administration through the skin was first achieved with hydrogel-type patches, that are polymer matrixes [4,22,61,75]. Matrix diffusion is characteristic... 

The transdermal route of drug administration offers several advantages over other methods of delivery. For some cases, oral delivery may be contraindicated, or the drug may be poorly absorbed. This would also include situations for which the drug undergoes a substantial first-pass effect [173] and systemic therapy is desired. 

This apparatus is primarily used for the transdermal patch. A variation of the apparatus is noted in a footnote in <724>. It is called the watchglass-patch-polytef mesh sandwich, and is favored by the US Food and Drug Administration (FDA) as the equipment of choice for transdermal patches. A diagram in Figure 16 illustrates how the system is assembled. 

Walters KA. Transdermal drug delivery. In Florence AT, Salole EG, eds. Routes of Drug Administration. London Wright, 1990 78-136. 

The development of the first transdermal patches in the 1980s generated considerable interest in this route of drug administration. Soon afterwards, iontophoresis was rediscovered and its potential to contribute to the new field of transdermal drug delivery was examined. This work provided the basic principles for modern iontophoretic devices [13,18-21]. Furthermore, and importantly, they demonstrated the existence of a (primarily) electroosmotic, convective solvent flux during transdermal iontophoresis [10,11,22-24], and it was shown that the permselective properties of the skin (a) could be exploited to enhance the transport of neutral, polar species and (b) have a clear impact on ionic transport. Subsequent research has better characterized skin permselectivity and the factors which determine the magnitude of electroosmosis [25-27],... 

A description of transdermal drug delivery has been produced which is based on the physicochemical properties of the permeant. At this time transdermal delivery is limited to the administration of potent drugs. Higher doses may be accessible if penetration enhancers are incorporated into the formulation. The kinetic model shows what properties these should have and that they are a function of the physico-chemical properties of the drug. Various loss processes, e.g. microbial biotransformation, skin enzyme metabolism can be identified but cannot, as yet, be quantified. 

Transdermal drug delivery is an attractive route of drug administration and will continue to proliferate in the following years. In the developmental stages it is important to have predictive models and to be able to identify suitable drug candidates. Although still in its infancy, the approach described above can be used predictively and as the mechanisms involved in percutaneous absorption are better understood and quantified the model can be refined accordingly. 

Recently, there is a growing recognition that the benefits of intravenous drug infusion can be closely duplicated, without its potential hazards, by using the intact skin as the portal of drug administration to provide a continuous transdermal drug delivery into the systemic circulation Q). 

International Pharmaceutical R D Symposium on Advances in Transdermal Controlled Drug Administration for Systemic Medications, Rutgers University, College of Pharmacy, June 20 21, 1985. 

Chien, Y. W. (1983), Logics for transdermal controlled drug administration, Drug Dev. Ind. Pharm., 9, 497-520. 

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