Transdermal delivery patches

Some effort was directed toward developing long-acting physostigmine preparations, and the transdermal delivery patches were especially promising [32]. The... 

F%.1 Venous blood concentrations in nanograms of nicotine per miUimeter of blood as a function of time for various nicotine delivery systems. Data on the cigarette delivering about 1 mg nicotine (filled square), oral snuff delivering 3.6 mg (filled circle), and 4 mg nicotine gum (star) are from those published by Benowitz et al. (1988). Data on 1 mg nicotine nasal spray (filled triangle) are from Schneider et al. (1996). Data on 21 mg transdermal nicotine patch (open square) are from Benowitz (1993). Data on the 4 mg nicotine lozenge (open circle) are from Choi et al. (2003)... 

Currently approved NRT products include the transdermal nicotine patch and several acute NRT products, including nicotine gum, lozenge, sublingual tablet, vapor inhaler, and nasal spray. The single-dose nicotine plasma curves for transdermal patch, gum, nasal spray, lozenge, as well oral snuff and a cigarette, are illustrated in Fig. 1 (note for the sake of simphcity, the curve for sublingual tablet is not illustrated, but because of the route of nicotine delivery, the plasma curve is qualitatively similar to nicotine gum). 

Cormier M, et al. Transdermal delivery of desmopressin using a coated microneedle array patch system. J Control Release 2004 97 503-511. 

Lin, W., et al. 2001. Transdermal delivery of antisense oligonucleotides with microprojection patch (Macroflux ) technology. Pharm Res 18 1789. 

PG fluxes into the receptor chamber following delivery across hairless mouse skin from formulations (a) and (b) are shown in Figures 3 and 4, respectively. PG association with EPC liposomes [(b)] lowers by one-half the transdermal delivery of the drug when compared to the free patch [(a)]. 

Figure 7.5 Melatonin kinetics after 10 h diurnal Cydot patch application in 12 healthy subjects. TMD =transmucosal delivery, TDD= transdermal delivery, ORAL-CR=oral controlled release delivery. (Courtesy of 3M Pharmaceuticals)...

Figure 8.3 Schematic diagrams of the three main categories of transdermal delivery system. It should be noted that these representations of the patches greatly exaggerate their real thicknesses, which are in fact similar to that of a normal Band-Aid...

Scopolamine was the first drug to be marketed as a transdermal delivery system (Transderm-Scop) to alleviate the discomfort of motion sickness. After oral administration, scopolamine has a short duration of action because of a high first-pass effect. In addition, several side-effects are associated with the peak plasma levels obtained. Transderm-Scop is a reservoir system that incorporates two types of release mechanims a rapid, short-term release of drag from the adhesive layer, superimposed on an essentially zero-order input profile metered by the microporous membrane separating the reservoir from the skin surface. The scopolamine patch is able to maintain plasma levels in the therapeutic window for extended periods of time, delivering 0.5 mg over 3 days with few of the side-effects associated with (for example) oral administration. 

These testosterone systems illustrate two different approaches to solve the problem of inadequate percutaneous absorption rate. In the former case, the patch must be applied to the body s most permeable skin site, the scrotum (which has been shown to be at least five times more permeable than ary other site). In the latter, the difficulty is resolved by creating a transdermal formulation which includes excipients to reduce barrier function. Neither solution is ideal scrotal application is clearly not preferred from a patient compliance standpoint on the other hand, permeation enhancers, by their very nature, tend to be irritating (and the more effective they are, the greater the irritation they provoke). This general problem, which presently limits the application of transdermal delivery, is now discussed in more detail. 

Nitroglycerin (NTC) is distinguished by a high membrane penetrability and very low stability. It is the drug of choice in the treatment of angina pectoris attacks. For this purpose, it is administered as a spray, or in sublingual or buccal tablets for transmucosal delivery. The onset of action is between 1 and 3 minutes. Due to a nearly complete presystemic elimination, it is poorly suited for oral administration. Transdermal delivery (nitroglycerin patch) also avoids presystemic elimination. 

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