Drug-in-adhesive type

In terms of the system design of TDS, there are three types of system constructions reservoir type, matrix type, and drug-in-adhesive type. In reservoir type and matrix type, pressure-sensitive adhesive (PSA) is only expected to keep the system on the skin. Hence, the necessary conditions for adhesives are almost the same as those of bandages, namely, well skin adhesiveness and low skin toxicity whereas in drug-in-adhesive type, the drug is incorporated into the adhesive so that the interaction between drugs and the PSA is more critical, as discussed later. 

Poultice is a drug-in-adhesive type of TDS and is very popular in Eastern countries. The hydrogel PSA is a base adhesive for poultice, as well as for skin care cosmetic sheets. A hydrogel adhesive is an ionically crosslinked polyacrylic acid swelling in a water-glycerin mixture. In addition, poultice formulation also... 

Two main types of transdermal patches are commonly used drug reservoir patch and drug-in-adhesive patch. Transdermal patches of early generations are mainly... 

Rgure 9.27 The four main types of transdermal patch matrix, reservoir, multilaminate and drug-in-adhesive designs. The matrix/reservoir systems are cut away to show the drug. Illustration courtesy of 3M. 

Kokubo, T., K. Sugibayashi, and Y. Morimoto. 1991. Diffusion of drug in acrylic-type pressure-sensitive adhesive matrices. I. Influence of physical property of the matrices on the drug diffusion. /. Contr. Rel. 17 69-78. 

This type of patch (scrotal patch Testoderm ) must be applied to dry, clean (shaven) scrotal skin, which is 5 to 30 times more permeable to testosterone than other skin sites, every 24 hours to produce an adequate testosterone plasma concentration. The matrix system is described as a drug-in-adhesive film, in which the drug is located on the adhesive layer of the film thus, it is thinner and less bulky than the reservoir system. The advantage of the matrix system is that it produces supraphysiological levels of DHT... 

The use of pressure-sensitive adhesives(PSAs) for skin-contact applications is discussed and the requirements of these adhesives in various applications are examined. Commercially-available classes of PSAs used for skin-contact applications include acrylics, polyisobutylenes and silicone polymers. Particular attention is paid in this review to transdermal drug delivery. The role of the PSAs in two types of transdermal designs is described and correlations between in-vivo and ex-vivo measurements of adhesion are discussed. Reports in the literature on human studies of various commercially-available transdermal systems are examined critically, with the aim of assessing the relative performance capabilities of each type of transdermal design. A list of currently commercialised transdermals is presented. 32 refs. 

The second type of device is a monolithic system (Fig. 9, middle) incorporating a backing layer, a matrix layer, and an adhesive layer. The matrix layer consists of a polymer material in which the solid drug is dispersed the rate at which the drug is released from the device is controlled by this polymer matrix. With this type of system, the drug release rate falls off with time as the drug in the skin-contacting side of the matrix is depleted. 

---