Patch adhesives

Adhesive patches are preferred over adhesive tablets because they are flexible and may be formulated in any shape. The size of the patehes may vary from 1 to 15 cm. Small patehes are more convenient and eomfortable to wear [27]. 

Adhesive ointments have not been investigated as extensively as have adhesive tablets or adhesive patches. Nevertheless, attempts have been made to utilize this dosage form primarily for local therapy [56]. 

Adhesive patches may also be monolithic or multilayered devices of the reservoir or matrix type for either systemic or local drug delivery (Fig. 8). The two main manufacturing processes to prepare adhesive patches are solvent casting and direct milling (with or without a solvent). The intermediate product is a sheet from which... 

In the preparation of adhesive patches by direct milling on a two-roll mill, the drug and the bioadhesive are homogeneously mixed with or without the aid of a solvent. The polymer/drug mixture may then be compressed to its desired thiekness and patches of appropriate size may be cut or punched out. The polymer/drug mixture prepared with a solvent may require an additional drying step by air or in an oven. 

Combined hormone replacement therapy is also available as self-adhesive patches and creams. 

V.a.1.2. Transdermal preparations. Adhesive patches applied to the skin can be used to deliver oestrogens transdermally, using either a reservoir of liquid or an oestradiol-containing matrix. These systems deliver adequate amounts of oestradiol to maintain plasma levels within the normal range for 24 hours, and some preparations now provide transdermal progestagen also, thus avoiding the need for additional tablets to be taken for part of the cycle. 

Korbonits M, Slawik M, Cullen D, Ross RJ, Stalla G, Schneider H, Reincke M, Bouloux P.M, Grossman AB. A comparison of a novel testosterone bioadhesive buccal system, Striant, with a testosterone adhesive patch in hypogonadal males. J Clin Endocrinol Metab 2004 89 2039-43. 

Novel approaches, such as the use of buccal adhesive patches for the systemic delivery of large molecular weight drags, require a huge input of time, effort and money, and are also associated with a large amount of risk. These issues can contribute to significant delay in the development and marketing of a new delivery system and can also make these systems relatively expensive. 

Recently, adhesive patches have been developed for transmucosal delivery. Such systems are discussed further in Section 7.7. 

Special formulations are now in development to provide prolonged mucosal adhesion and sustained delivery of drug through the buccal membrane. Such formulations comprise flexible adhesive patches and films. Important features for drug delivery associated with these novel buccal patches include ... 

For drugs absorbed via passive diffusion mechanisms (paracellular or transcellular), increasing the area of the patch should increase the amount of drug absorbed. However, patch size must always be considered with respect to patient comfort and acceptability and must not be too large so that these factors are compromised. Thus the size of adhesive patches is generally in the range 2-5 cm2, with 10-15 cm2 being the upper limit. 

Poor compliance with traditional patching Hypersensitivity or skin allergies resulting from adhesive patch... 

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