Transdermal Drug Delivery Devices

Conventionally, drugs are administered either orally or by injection. Unfortunately, many medicaments are completely ineffective or have radically reduced efficacy when orally administered since they either are not absorbed or are adversely affected before entering the bloodstream and thus do not possess the desired activity (45). On the other hand, the direct injection of the medicament into the bloodstream, while assuring no modification of the medicament during administration, is a difficult, inconvenient, painful and uncomfortable procedure, sometimes resulting in poor patient compliance. 

The transdermal route of agent administration could be advantageous in the delivery of many therapeutic proteins, because proteins are susceptible to gastrointestinal degradation and exhibit poor gastrointestinal uptake, and transdermal devices are more acceptable to patients than injections. 

However, the transdermal flux of medically useful peptides and proteins is often insufficient to be therapeutically effective due to the large molecular weight. 

Transdermal drug delivery systems generally rely on passive diffusion to administer the drug, while active transdermal drug delivery systems rely on an external energy source to deliver the drug. 

Passive transdermal drug delivery systems are more common. Passive transdermal systems have a drug reservoir containing a high concentration of drug adapted to contact the skin, where the drug 

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Govil SK. Transdermal drug delivery devices. In Tyle P, ed. Drug Delivery Devices. Fundamentals and Applications. New York Marcel Dekker, 1988 386 19. 

U. S. Patent 5,698,217 Wilking, S. L. Transdermal Drug Delivery Device Containing a Dessicant. December 16,1997. 

Govil SK. Transdermal drug delivery devices. In Tyle P, ed. Drug Delivery Devices. Fundamentals and Aprplications, 1st edn. New York Marcel Dekker, 1988 386 19. Walters KA. Transdermal drug delivery. In Florence AT, Salole EG, eds. Routes of Drug Administration, 1st edn. London Wright, 1990 78-136. 

In 1992 the 3 M disclosed blends that comprised 100 parts VLDPE [Flexomer or Attane 80-95 mol% ethylene and 5 mol% C4 g comonomer(s)] and 15-600 parts m-LLDPE [DOWLEX ethylene copolymer with 2-8 mol% Cg]. The blends showed excellent processability. Formed into 10-300 pm thick films, they were used for transdermal drug delivery devices as single-layer backings. The films were clear, colorless, transparent to visible light, and sealable at relatively low temperature. They were permeable to O2, stable to various common components of transdermal delivery devices, strong, and comfortable and did not absorb significant amounts of common elements of transdermal carriers (Godbey and Martin 1993, 1994). 

M.J.N. Cormier, W.A. Young, K. Nyam, RE. Daddona, and W.-Q. Lin, Transdermal drug delivery devices having coated microprotrusions, US Patent 8663155, assigned to Alza Corporation (Vacaville, CA), March 4,2014. 

CL Armstrong, HGM Edwards, DW Farwell, AC Williams. FT-Raman microscopic study of drug distribution in a transdermal drug delivery device. Vibr Spectrosc 11 105-113, 1996. 

Barry B. Novel mechanisms and devices to enable successful transdermal drug delivery. Eur J Pharm Sci 2001 14 101-114. 

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],... 

Good, W. Transdermal drug delivery systems. Medical Device Diagnostic Industry. 2 35-42, 1986. 

This section focuses on adhesives that are used for the assembly of medical devices. In medical device assembly, the primary substrates are plastics, elastomers, and metals. The total medical adhesive market is much larger since it encompasses a broader definition of products. For example, medical adhesives can be used for bonding human tissue, transdermal drug delivery systems, dental restoration, and wound care in addition to medical device assembly. 

Whenever a drug-delivery device such as an insecticidal collar or a transdermal system is securely placed on an animal, the increased potential for drug interaction must be kept in mind at the time of selecting another drug for administration by any route and throughout the course of therapy. 

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