Transdermal drug delivery composition

Silicone functionalized PIB is particularly suitable as a pressure sensitive adhesive composition in medical applications including transdermal drug delivery applications (83). 

The results are reported of an investigation into the stability, in-vitro drug delivery and adhesive properties of drug-in-adhesive transdermal drug delivery systems. These systems are composed of a flexible backing film, a fluoropolymer release liner and active adhesives, which vary in their monomeric compositions and functionalities. The adhesives are composed of an acrylic pressure-sensitive adhesive, an amine-compatible silicone pressure-sensitive adhesive and methylphenidate base, as the drug. 4 refs. 

Table 1 Effect of chemical enhancers and vehicle composition on the transdermal passive delivery of peptide drugs...

The term parenteral drug delivery covers a number of administration routes which have little in common other than the fact that they generally involve the use of a hypodermic needle to inject the drag into the body. This route of administration bypasses a number of physiological barriers. The constraints on the composition and formulation of the medicine are much more rigorous than for less invasive routes such as oral or transdermal delivery. Despite this, a surprising range of materials can be injected into various tissues if the appropriate precautions are taken. 

Other than possibly for the insensible perspiration they absorb, transdermal patches tend to operate as thermodynamically static systems, meaning as com-positionally fixed systems, from the moment they are applied until their removal. Marketed ethanol-driven estradiol and fentanyl patches are exceptions because they meter out ethanol and drive it into the stratum corneum to propel the absorption process. Compositional steadfastness is still the rule, however, and it is this feature that bestows the zero-order delivery attribute on the ordinary transdermal patch. Drug is present within the patches in reservoir amounts whether or not the reservoir compartment is easily distinguished, for there must be enough drug to sustain delivery over the full course of patch wear. 

Dermal and transdermal delivery requires efficient penetration of compounds through the skin barrier, the bilayer domains of intercellular lipid matrices, and keratin bundles in the stratum corneum (SC). Lipid vesicular systems are a recognized mode of enhanced delivery of drugs into and through the skin. However, it is noteworthy that not every lipid vesicular system has the adequate characteristics to enhance skin membrane permeation. Specially designed lipid vesicles in contrast to classic liposomal compositions could achieve this goal. This chapter describes the structure, main physicochemical characteristics, and mechanism of action of prominent vesicular carriers in this field and reviews reported data on their enhanced delivery performance. 

Jamstrom, R. Hirvonen, J. Composition for Transdermal Delivery of Drugs. US Patent 6,254,883, July 3, 2001. 

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