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Transdermal PatchesTransdermal patch is a medicated adhesive pad that is placed on the skin to deliver a time-release portion of medication through the skin into the bloodstream. It is also called skin patch. The patches represent an attractive alternative to conventional formulations. Transdermal drug delivery  Transdermal delivery means transport of the drug through the skin for systemic effect. It is the non-invasive method and avoids many problems of conventional injection and oral routes. It reduces the load the digestive tract and liver, enhances patient compliance, and minimizes the likelihood of overdose. Simple application can aid in patient adherence. However, there is a small obstacle: the main function of skin is preventing things entering our body. The application of transdermal delivery to a wide range of drugs is limited due to the significant barrier to penetration across the skin. Significant effort has been devoted to developing strategies to overcome the impermeability of intact human skin. These strategies include passive and active penetration enhancement and technologies to bypass the stratum corneum. Main components The development of transdermal systems is a complex process. There are several designs of delivery systems in patches: reservoir, matrix, drug-in-adhesive. These designs are composed of five layers:
Transdermal patches The history of plasters has been traced from old times. The mustard plaster, applied for chest congestion, may be an example. Transdermal patches were developed in the 1970s and the first was approved by the FDA in 1979 for the treatment of motion sickness. It was a three-day patch that delivered scopolamine. A decade later, nicotine patches became the first transdermal blockbuster. Today, drugs administered through the skin patches include clonidine, testosterone, oxybutinin, methylphenidate, scopolamine (for motion sickness), nicotine (for quitting smoking), estrogen (for menopause and to prevent osteoporosis after menopause), nitroglycerin (for angina), fentanyl, and lidocaine (local anesthetic). Molecules of insulin and many other substances, however, are too large to pass through the skin. It is estimated that more than one billion transdermal patches are currently manufactured each year. The major advantages provided by transdermal delivery systems include the following: improved bioavailability, steady absorption and more uniform plasma levels, shortened metabolization pathway, and reduced side effects. Additionally, transdermal patches allow the avoidance of partial first-pass inactivation of the drug by the liver and pH associated deactivation. They can provide release for long periods of time (up to one week). Their effects can be rapidly terminated via removal. Transdermal delivery also has advantages over injections, which are painful, generate dangerous waste, and pose the risk by needle re-use. How to use skin patches Carefully remove the patch from its pouch, taking care not to tear the patch. Use your fingers rather than scissors to avoid damaging the patch. Pull off the plastic backing to expose the adhesive. Do not touch the sticky surface of the patch. Apply the patch firmly with the sticky side down to a clean, dry, non-hairy area of skin, on the area of the body as specified in the instructions on how to use your patch. Do not apply it to broken or irritated skin or spots. Don't put moisturiser, creams or powder on the skin before applying the patch, as this may stop it from sticking properly. When applying a new patch, remove the old one first and apply the new one to a slightly different area. This avoids irritating the skin. To remove the patch, peel off one corner and pull the patch smoothly away from the skin. Any glue or sticky residue left on the skin can be removed with baby oil. If a patch falls off, replace it with a new one and keep to your patch change days as normal. If you have just had a bath or shower wait for the skin to cool down before applying a new patch. Try to avoid wearing the patch under tight clothing or elasticated waistbands. If you sunbathe while wearing the patch, cover the patch so it is not exposed to direct sunlight. Exercising or applying heat to the patch may increase the amount of the active ingredient absorbed into the body. This can increase the risk of side effects. Never divide or cut a patch. References
Last updated: January, 2011 |
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