Drugs can be delivered across the skin to have an effect on the tissues adjacent to the site of application (topical delivery) or to have an effect after distribution through the circulatory system (systemic delivery). While there are many advantages for delivering drugs through the skin the barrier properties of the skin provide a significant challenge. By understanding the mechanisms by which compounds cross the skin it will be possible to devise means for improving drug delivery. In the last decades, transdermal dosage forms have been introduced for providing a controlled delivery via the skin into the circulation system.
A transdermal patch or skin patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the blood stream. Drug-in-adhesive-type patches have been gaining increasing popularity as effective transdermal delivery systems during the last two decades due to various advantages over other systems namely, they are easy to construct, less chances of dose dumping and patches with less thicknesses can be prepared.
Diclofenac is a well-established non-steroidal anti-inflammatory agent, widely used in musculoskeletal disorders, arthritis, toothache, dysmenorrhea, etc., for symptomatic relief of pain and inflammation. Diethylammonium salt of Diclofenac (Diclofenac Diethylamine) is reportedly used for topical applications. Diclofenac Diethylamine (DDEA) gel (1.16%; Voltaren® Emulgel®, Novartis, Nyon, Switzerland) has been used extensively in Europe since 1985 to relieve the symptoms of OA of the knee, as well as other painful, inflammatory tendon, ligament, muscle, and joint conditions. However, all NSAIDs include a boxed warning highlighting the potential for increased risk of cardiovascular events as well as serious potential life-threatening gastrointestinal bleeding. The drug undergoes substantial hepatic first-pass metabolism and thus only about 50% of the administered dose reaches systemic circulation[3, 5]. This originates the need of an alternative route of administration, which can bypass the hepatic first-pass metabolism. Transdermal route is an alternative choice of route of administration for such drugs. The drug, Diclofenac Diethylamine also possesses the ideal characteristics, such as poor bioavailability (40 to 60%), short biological half-life (2 to 3 h), smaller dose (25 to 50 mg), etc., to be formulated into a transdermal patch. Transdermal patches offer added advantages, such as maintenance of constant and prolonged drug level, reduced frequency of dosing, minimization of inter and intra patient variability, self-administration and easy termination of medication, leading to patient compliance.
It has been postulated that Diclofenac transdermal exerts its pharmacological effects through localized accumulation at the site of application rather than from the systemic absorption. The bioavailability of Diclofenac transdermal is approximately 1% that of oral Diclofenac, with an elimination half-life of 12 h compared with 1.2 to 2 h with oral Diclofenac.
The present study aimed at developing TDDS drug-in-adhesive patches of DDEA using Silicone adhesives, Acrylic adhesives and blend of Silicone and Acrylic adhesives.