Transdermal systems materials

The higher viscosity of semisolid dosage forms and transdermal systems may cause the rate of migration of leachable substances into these dosage forms to be slower than for aqueous solutions. Due to extended contact, the amount of leach-ables in these drug products may depend more on a leachable material s affinity for the liquid/semisolid phase than on the rate of migration. 

Table 7 outlines general expectations associated with transdermal delivery and compares with those associated with topical deUvery. The water-impermeable backing materials of present and presumably most future transdermal systems make them occlusive. Impermeable polymer or foil backings also block the diffusive transport of body water to the atmosphere by way of the patch. Insensible perspiration at the site of the patch is thus held in check, but not without creating a substantially moist environment at the interface the patch has with the skin. Consequently, if given enough time, organisms already in the skin can colonize within this interface. 

Scheme 2 Some possibilities for the pharmaceutical technologies and approaches to be used in personalized medicine, ranging from simple liquid oral dose forms where the dose can be varied by volume, through responsive systems, micro-electromechanical systems (MEMS), GPS-directed systems (see text) transdermal systems, thin film technologies with passive or active release mechanisms, combination tablet or capsule dose forms, and what we term dosed solid platforms, for example, aqueous dispersible polymer, solid gel or matrix material into which precise doses of drag can be absorbed.

Hye Kim, J., Kim, S., Kwon, 1. B., Hyun Kim, M., 1. K., Lim, J. (2013). Simple fabrication of silver hybridized porous chitosan-based patch for transdermal drug-delivery system. Materials Letters. 95, 48-51. 

Up to now, the development of microneedles has focused on microfabrication techniques for Si and other biocompatible materials. Currently, there are several commercially available microneedle products, such as MTS (Microstructured Transdermal System) by 3 M, Macroflux by ALZA, and Micro-Trans by Bio Valve Technologies, and most of them are designed to increase skin permeability and adopt passive delivery methods (i.e., capillary force). As the feasibility of microneedles is well established, the next step is to understand the characteristics of fluid transport by microneedles,... 

The applications of hydrogels in the production of medical items, resulting materials must have several features, which recommends them non-toxicity, functionability, sterilizability, biocompatibUity [115]. These characteristics are requires for wound dressings, drug delivery systems, transdermal systems, injectable polymers, implants, dental and ophthalmic applications, stimuli-responsive systems, hydrogel hybrid-type organs. 

Uses Emulsifier, solubilizer for fat-sol. vitamins, essential oils, and hydrophobic materials in pharmaceuticals (tablets, capsules, orals, topicals, sprays, ointments, creams, lotions, gels, suppositories, transdermal systems) emulsifier, solubilizer for essential oils and perfumery in cosmetics Features Chemically very stable largely insensitive to water hardness Regulatory EP, USP/NF compliance... 

Fig. 4. Cross-section of a reservoir type of transdermal dmg deUvery system. The backing material and heat seals at the periphery of the system prevent loss...

Allergic contact dermatitis from transdermal estrogen has been described in Korea, where the reaction was found to be due to 17-P-estradiol itself and not to an excipient (226). In some cases, allergic reactions and systemic contact dermatitis are clearly attributable to the patch material or to excipients. Even natural estradiol given in this way can occasionally cause hypersensitivity reactions, as determined by patch tests (227). 

Approved packaging is normally selected after completing package performance qualification testing as well as product compatibility and stability studies. Since in most cases (exceptions transdermal delivery systems, diagnostic tests, and medical devices) packaging is not intimately involved in the manufacturing process of the product itself, it differs from other factors, such as raw materials. 

Figure 10.1 contains an illustration of an implanted fluorescence-based sensor assuming the implanted materials and monitoring system can be designed to have each of the properties described above, this configuration is ideal, as it does not require any transdermal connections or implanted electronics. 

Membrane-reservoir systems based on solution-diffusion mechanism have been utilized in different forms for the controlled delivery of therapeutic agents. These systems including membrane devices, microcapsules, liposomes, and hollow fibres have been applied to a number of areas ranging from birth control, transdermal delivery, to cancer therapy. Various polymeric materials including silicone rubber, ethylene vinylacetate copolymers, polyurethanes, and hydrogels have been employed in the fabrication of such membrane-reservoir systems (13). 

Nitto Denko Corporation primarily manufactures industrial adhesive tapes for the electronics, automotive, health care, packaging and construction industries. The company produces industrial, electronic and functional products. Industrial products include double-coated adhesive tapes, masking tapes surface protective materials, sealing materials and label printing systems. Electronics products include LCD-related items general and advanced device resins printed circuit boards and semiconductor package adhesive sheets. Functional products include medical items such as transdermal therapeutic patches polymer separation membranes used for water purification and treatment and plastic engineering products such as information equipment and porous film materials used in cars, electronics, and home appliances. Nitto Denko America, Inc., an optoelectronics subsidiary, manufactures semiconductor... 

In terms of overall composition, traditional transdermal patch systems have changed little in the past few years. The modifications that have been made are, for the most part, refinements of the materials used in their construction (Table 3). This is the case for the soft patches that consist of thin flexible films containing a known amount of drug. The soft patch is designed to be flexible and to conform to various body flexures. 

Efficient iontophoretic delivery depends on the materials and excipients used in the system. Selection of appropriate electrodes and formulations are critical to maximizing the efficiency of iontophoretic treatments. The following sections will summarize key criteria for selection of electrodes and formulations for transdermal applications, however, many of the same principles are applicable to iontophoretic systems used on mucosa or implanted within the body. 

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