Transdermal therapeutic design

There are three techniques used for the transdermal administration of fentanyl. The transdermal therapeutic system (TTS) is a membrane-controlled system designed... 

A transdermal therapeutic system is a rate-controlled drug delivery system which, applied to the surface of the skin, continuously releases the drug at a rate that will provide a desired steady-state plasma concentration for a specified duration. A candidate drug must possess high activity (i.e. be effective at low plasma concentrations) and efficiently penetrate the stratum comeum-, percutaneous absorption must be reliably consistent. Based on technological design there are four types of rate-controlled transdermal drug delivery system (Chien, 1987) ... 

Chandrasekaran, S. K., Shaw, J. E. Design of transdermal therapeutic systems, in Contemporary topes in polymer science, VoL 2. Pearce, E. M., Schaefgen, J. R. (eds.). New York Plenum Press 1977... 

There are several available transdermal therapeutic systems including reservoir membrane designs and, as will be discussed in subsequent sections, matrix designs. A typical reservoir transdermal therapeutic system is shown in Figure 16. 

Cross-sectional diagram of the design of a reservoir transdermal therapeutic (patch) system... 

Transdermal delivery is a noninvasive intravenous infusion of drug to maintain efficacious drug levels in the body for predictable and extended duration of activity. Diffusion-controlled transdermal systems are designed to deliver the therapeutic agent at a controlled rate from the device to and through the skin into the systemic circulation. This route of administration avoids unwanted presystemic metabolism (first-pass effect) in the GI tract and the liver. Patient satisfaction has been realized through decreased... 

The route of administration influences the likelihood of an antibody response independent of the mechanism of induction. The probability of an immune response is the highest with subcutaneous administration, less probable after intramuscular administration and intravenous administration is the least immunogenic route. There are no studies comparing parenteral and nonparenteral routes of administration. Flowever, as both mucosal tissues and the skin are immune competent organs designed to keep invaders out of the body, intranasal, pulmonary, and transdermal administration of therapeutic proteins may increase the risk of an immune response as compared to parenteral routes. 

Given the limitations imposed on transdermal systemic drug delivery by the barrier properties of the stratum corneum, new technologies have attempted to completely bypass this obstacle by either the creation of a physical conduit (microneedles) or direct powder delivery via compressed gas. The Alza Corporation technology (Macroflux ) comprises a patch system that contains a microprojection array designed to create superficial microchannels across the stratum corneum.When used in conjunction with their electrotransport system, the Macroflux system provides controlled in vivo delivery of therapeutic doses of... 

Application of SCF is now the subject of increasing interest especially in the pharmaceutical industry and there are three aims increasing bioavailability of poorly soluble molecules designing sustained-release formulations and formulation of active agents for new types of drug delivery that are less invasive than parental delivery (oral, pulmonary, transdermal). The most complex challenge is related to therapeutic delivery, as it is extremely difficult to obtain a satisfactory therapeutic delivery effect due to biomolecule instability and very short half-life in vivo. 

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