Abstract: The skin is very effective as a selective penetration barrier. Percutaneous absorption involves the passage of the drug molecule from the skin surface into the stratum corneum under the influence of a concentration gradient and its subsequent diffusion through the stratum corneum and underlying epidermis, through the dermis, and into the blood circulation. There is currently a great deal of world-wide interest in the field of transdermal drug delivery and, consequently, broad classes of drugs are being evaluated for percutaneous absorption potential. The advantages of this mode of drug administration are numerous, the patient convenience and therapeutic optimization of using patch transdermal systems being major positive features. The in vitro release test is a measure of in process control and also as a finished product specification for example, gels, emugel and spray. An in vitro diffusion cell experiment was designed to demonstrate the rate of release of Diclofenac sodium from three different topical formulations: (i) gels, (ii) emugel and (iii) spray. In vitro release of Diclofenac sodium from three different formulations through the receptor phase through human cadaver skin was monitored chromatographically. By monitoring and attempting to explain the numerous possible from the three formulations, it was a better to understanding of the complexities of transdermal drug administration. More over spray topical formulation could be suggested as a good dosage form for the topical delivery of Diclofenac sodium, giving higher drug release than the gel and emugel formulations.

 
Introduction: The skin is the largest human organ. It ensures that harmful substances and drugs released from topically applied formulations cannot intrude into the organism offhand [1]. Drug delivery through the skin has been used to target the epidermis, dermis and deeper tissues and for systemic delivery. The major barrier for the transport of drugs through the skin is the stratum corneum, with most transport occurring through the intercellular region. When taken orally, many drugs are destroyed by the liver. Drug administration through the skin often pro-vides a slower, more controlled alternative route for release into the blood stream. There is currently a great deal of world-wide interest in the field of trans-dermal drug delivery and, consequently, broad classes of drugs are being evaluated for percutaneous absorption potential. Another potential ad-vantage of this type of drug delivery is the optimization of drug concentration at the desirable sites, reducing the chances of side effects [2]. Therapeutic efficacy of any topical formulation depends on its ability to deliver drugs to their sites of action from the skin surface for either local or systemic purposes. [3, 4]. Diclofenac sodium (2-[2-[(2, 6-dichlorophenyl) amino] phenyl] acetic acid) is a potent member of non-steroidal anti-inflammatory drugs (NSAIDS) and widely used clinically, because of its strong analgesic and anti-pyretic effect [5].It has a short half-life (2 hrs). Diclofenac sodium causes gastrointestinal disturbances, peptic ulceration with bleeding, if present in large doses in gastrointestinal tract [6].It is marketed as injections, oral sustained release tablets and topical formulations. After oral administration, it is extensively metabolized in the liver and because of its short biological half-life, the drug has to be administered frequently [7]. The topical application allows for a higher local concentration of the drug at the site of initiation of the pain and lower or negligible systemic drug levels producing fewer or not adverse drug effects [8]. Topical drugs used to control pain act locally on damaged or dysfunctional soft tissues or peripheral nerves, and their actions may be on the inflammatory response itself or on sensory neurons [2]. A Diclofenac formulation with a high degree of skin permeation could be useful in the treatment of not only locally inflamed skin tissues, but also inflammatory and painful states of supporting structures of the body bones, ligaments, joints, tendons and muscles [9, 10]. The present work aims to evaluate that in vitro release of Diclofenac sodium from the different formulations.