Transdermal patches rate-controlling membrane

Membrane-moderated patches have been utilized in many FDA-approved transdermal patches such as Duragesic, Transderm Scop, and Catapress TTS. This type of patch utilizes a rate-controlling membrane to precisely control the release of... 

The transdermal dmg formulations could be in the form of a suspension, solution, gel, ointment, or multilayer transdermal patch. A controlled dmg release from the patch is usually achieved by changing the properties of either the rate-controlling membrane or the dmg matrix. 

Experimental transdermal patches have also been fabricated by flanking a solution or gel containing the test drug and other excipients between an impermeable backing laminate and a rate-controlling membrane. A pressure-sensitive adhesive coated on the membrane ensures an intimate patch-skin cmitact. The patch is kept in a sealed aluminum pouch to minimize solvent loss [31, 62, 64]. 

Fig. 45. Schematic of transdermal patch in which the rate of deUvery of dmg to the body is controlled by a polymer membrane. Such patches are used to...

Controlled release can be achieved by a wide range of techniques a simple example, a transdermal patch, is illustrated in Figure 49. In this device, a drug is held in a reservoir surrounded by a membrane. With such a system, the release rate of drug is constant as long as a constant concentration of drug is maintained within the device. Such a constant concentration is maintained if the reservoir contains a saturated solution and sufficient excess of solid drug. Systems that... 

There is a wide variety of transdermal systems on the market at present. These patches are diversely referred to as reservoir , monolithic , membrane-controlled , adhesive , matrix , and so on. Unfortunately, these terms are not always used consistently and, worse, they are sometimes used inaccurately. In all cases, however, the idea is that the system offers a means to hold a payload of the drag and a configuration (or platform ) to ensure presentation of the active agent to the skin surface at a rate sufficient to ensure a systemic pharmacological effect after the drag has crossed the skin s barrier. Most simplistically, one can divide the transdermal formulations presently available into three categories (Figure 8.3) ... 

Transdermal scopolamine is a muscarinic receptor antagonist used for the prevention of post-operative nausea and vomiting. It is supplied as a circular adhesive patch (0.2 mm thick and 2.5 cm ) applied to the post-auricular skin. Each patch contains 1.5 mg of the belladonna alkaloid programmed to continuously release in vivo approximately 1.0 mg over 72 hours. The patch consists of four distinctive layers. Going from visible surface to the surface adherent to the skin, these layers are (1) backing layer (2) drug reservoir of scopolamine (3) microporous polypropylene membrane that controls the rate of scopolamine delivery (4) adhesive contact surface with the skin. 

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