RECENT ADVANCEMENT IN TRANSDERMAL DRUG DELIVERY SYSTEM Review Article KHUSHBU ANSARI 1 , A. K. SINGHAI 1 , GAURAV. K. SARAOGI 1 1 Lakshmi Narain College of Pharmacy, Kalchuri Nagar, Bhopal, (M.P.) India. Email: khushbuansari1may@gmail.com Received: 26 Aug 2011, Revised and Accepted: 6 Oct 2011 ABSTRACT There is considerable concern in the skin as a site of drug application both for local as well as for systemic effect. However, the skin, in particular the stratum corneum, poses a formidable obstacle to drug penetration thereby limiting topical and transdermal bioavailability. Transdermal drug delivery systems (TDDS) involve penetration enhancement techniques to improve bioavailability and increase the range of drugs for which topical and transdermal delivery is a viable option. TDDS differs from traditional drug delivery & had many advantages over conventional dosage forms such as non-invasive, ease of use, withdrawal (increase of side effect), avoidance of first pass metabolism, better patient compliance. However, the major limitation of this route is difficulty of permeation which can be overcome by using different combination of permeation enhancer’s. This review article provides an overview of types of transdermal patches, method of preparation & its evaluation parameters. Keywords: Transdermal delivery, Patches, Drug delivery systems, Topical delivery INTRODUCTION Conventional systems of medication which require multidose therapy have numerous problems and complications. The design of conventional dosage form, whether a tablet, an injection or a patch, to deliver the right amount of medicine at the right target site becomes complicated if each medication were to be delivered in an optimal and preferred manner to the individual patient. The impetus for the development of novel drug delivery systems, apart from therapeutic efficacy is cost. Redesigning the modules and means to transport medicine into the body is less demanding and more lucrative task. To address these problems, controlled release drug delivery system, a novel drug delivery approach evolves, which facilitates the drug release into systemic circulation at a pre- determined rate. Controlled drug release can be achieved by transdermal drug delivery systems (TDDS) which can deliver medicines via the skin portal to systemic circulation at a predetermined rate over a prolonged period of time 1 Optimum therapeutic outcomes require not only proper drug selection but also effective drug delivery. The human skin is a readily accessible surface for drug delivery. Controlled drug delivery has become increasingly important in the pharmaceutical industry now- a-days. The pharmacological response, both the desired therapeutic effect and the undesired adverse effect, of a drug is dependent on the concentration of the drug at the site of action, which in turn depends upon the dosage form and the extent of absorption of the drug at the site of action. Skin of an average adult body covers a surface of approximately 2 m . 2 and receives about one-third of the blood circulating through the body. Skin contains an uppermost layer, epidermis which has morphologically distinct regions; basal layer, spiny layer, stratum granulosum and upper most stratum corneum, it consists of highly cornified (dead) cells embedded in a continuous matrix of lipid membranous sheets 1,2 . These extracellular membranes are unique in their compositions and are composed of ceramides, cholesterol and free fatty acids. The human skin surface is known to contain, on an average, 10-70 hair follicles and 200-250 sweat ducts on every square centimetres of the skin area. It is one of the most readily accessible organs of the human body. The potential of using the intact skin as the port of drug administration to the human body has been recognized for several decades, but skin is a very difficult barrier to the ingress of materials allowing only small quantities of a drug to penetrate over a period of time. Transdermal drug delivery—the delivery of drugs across the skin and into systemic circulation—is distinct from topical drug penetration, which targets local areas 2 Transdermal drug delivery system is a formulation or device that maintains the blood concentration of the drug within the therapeutic window ensuring that drug levels neither fall below the minimum effective concentration MEC nor exceed the minimum toxic dose . 3 Aim of TDDS . For transdermal products the goal of dosage design is to maximize the flux through the skin into the systemic circulation and simultaneously minimize the retention and metabolism of the drug in the skin 1 The steady permeation of drug across the skin allows for more consistent serum drug levels, often a goal of therapy . 2 Advantages of Transdermal Drug Delivery . 1. Avoidance of peak-and-trough blood concentrations associated with conventional oral administration. 4 2. Avoidance of first-pass metabolism in the gastrointestinal tract. 3. Reduced variability of absorption between and within patients. 4. Prolonged duration of action after application of one dosage form and lower frequency of dosing. 5. Improved compliance (particularly of drugs with short half- lives). 6. Concentration-dependent selectivity of drug action. 7. Drowsiness, confusion and blurred Vision, and have a relatively short duration of action. 8. Rate-controlled delivery might prolong the effect and minimize these adverse effects. Disadvantages of Transdermal Drug Delivery 4 The possibility of local irritation may develop at the site of application like Erythema, itching, and local oedema can be caused by the drug, the adhesive, or other excipients from the patch formulation. For most patients, site rotation can minimize irritation. However, some patients develop severe allergic reactions to transdermal patches, and in these cases, therapy must be discontinued. It is that the skin's low permeability limits the number of drugs that can be delivered in this manner. Because the skin serves protective functions, it inhibits compounds from crossing it. Many drugs with a hydrophilic structure permeate the skin too slowly to be of therapeutic benefit. Drugs with a lipophillic character, however, are better suited for transdermal delivery. Many of the recent developments in transdermal drug delivery target the more hydrophilic compounds that were previously undeliverable via this method. Damage to a transdermal patch, particularly a membrane or reservoir patch, can result in poor control over the release rate. The release rate International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 3, Suppl 5, 2011 A A c c a a d d e e m mi i c c S Sc c i i e e n nc c e e s s