| Drug delivery technologies are now receiving | | | | |
| considerable attention from pharmaceutical | | | | The main components of a transdermal patch |
| companies. The main purpose of developing | | | | are: Transdermal patch may include the |
| alternative drug delivery technologies is to | | | | following components: |
| increase efficiency and safety of drug | | | | |
| delivery and provide more convenience for the | | | | Liner - Protects the patch during storage. |
| patient. Substantial research conducted | | | | The liner is removed prior to use. |
| during the past several years has lead to the | | | | |
| development of technologies that meet the | | | | Drug - Drug solution in direct contact with |
| requisite criteria for delivering the drug | | | | release liner |
| through a non-invasive route. One of such | | | | |
| technologies is transdermal drug | | | | Adhesive - Serves to adhere the components |
| delivery.Transdermal drug delivery is the | | | | of the patch together along with adhering the |
| non-invasive delivery of medications from the | | | | patch to the skin |
| surface of the skin - the largest and most | | | | |
| accessible organ of the human body - through | | | | Membrane - Controls the release of the drug |
| its layers, to the circulatory system. | | | | from the reservoir and multi-layer patches |
| Medication delivery is carried out by a patch | | | | |
| that is attached to the body surface. | | | | Backing - Protects the patch from the outer |
| Transdermal patch is a medicated adhesive pad | | | | environment |
| that is designed to release the active | | | | |
| ingredient at a constant rate over a period | | | | Types of transdermal patchesThere are four |
| of several hours to days after application to | | | | main types of transdermal |
| the skin. It is also called skin patch. A | | | | patches:Single-layer Drug-in-Adhesive In this |
| skin patch uses a special membrane to control | | | | system the drug is included directly within |
| the rate at which the drug contained within | | | | the skin-contacting adhesive. In this type of |
| the patch can pass through the skin and into | | | | patch the adhesive layer is responsible for |
| the bloodstream.The first transdermal patch | | | | the releasing of the drug, and serves to |
| was approved by the FDA in 1979. It was a | | | | adhere the various layers together, along |
| patch for the treatment of motion sickness. | | | | with the entire system to the skin. The |
| In the mid-1980s, the pharmaceutical | | | | adhesive layer is surrounded by a temporary |
| companies started the development of a | | | | liner and a backing.Multi-layer |
| nicotine patch to help smokers quit smoking, | | | | Drug-in-AdhesiveThe Multi-layer |
| and within a few months at the end of 1991 | | | | Drug-in-Adhesive is similar to the |
| and beginning of 1992 the FDA approved four | | | | Single-layer Drug-in-Adhesive in that the |
| nicotine patches.Today drugs administered | | | | drug is incorporated directly into the |
| through skin patches include scopolamine (for | | | | adhesive. The multi-layer system adds another |
| motion sickness), estrogen (for menopause and | | | | layer of drug-in-adhesive, usually separated |
| to prevent osteoporosis after menopause), | | | | by a membrane. This patch also has a |
| nitroglycerin (for angina), lidocaine to | | | | temporary liner-layer and a permanent |
| relieve the pain of shingles (herpes zoster). | | | | backing.ReservoirThe Reservoir transdermal |
| Non-medicated patches include thermal and | | | | system design includes a liquid compartment |
| cold patches, weight loss patches, nutrient | | | | containing a drug solution or suspension |
| patches, skin care patches (therapeutic and | | | | separated from the release liner by a |
| cosmetic), aroma patches, and patches that | | | | semi-permeable membrane and adhesive. The |
| measure sunlight exposure.Advantages and | | | | adhesive component of the product can either |
| disadvantages of transdermal drug delivery | | | | be as a continuous layer between the membrane |
| | | | and the release liner or as a concentric |
| Transdermal drug delivery systems offer | | | | configuration around the membrane.Matrix The |
| several important advantages over more | | | | Matrix system has a drug layer of a semisolid |
| traditional approaches, including: | | | | matrix containing a drug solution or |
| | | | suspension, which is in direct contact with |
| | | | the release liner. The adhesive layer in this |
| | | | patch surrounds the drug layer partially |
| longer duration of action resulting in a | | | | overlaying it.The future of transdermal drug |
| reduction in dosing frequency | | | | deliveryTransdermal drug delivery is |
| | | | theoretically ideal for many injected and |
| Increased convenience to administer drugs | | | | orally delivered drugs, but many drugs cannot |
| which would otherwise require frequent dosing | | | | pass through the skin because of skin's low |
| | | | permeability. Pharmaceutical companies |
| | | | develop new adhesives, molecular absorption |
| improved bioavailability | | | | enhancers, and penetration enhancers that |
| | | | will enhance skin permeability and thus |
| more uniform plasma levels | | | | greatly expand the range of drugs that can be |
| | | | delivered transdermally.Two of the |
| reduced side effects and improved therapy | | | | better-known technologies that can help |
| due to maintenance of plasma levels up to the | | | | achieve significant skin permeation |
| end of the dosing interval | | | | enhancement are iontophoresis and |
| | | | phonophoresis (sonophoresis). Iontophoresis |
| flexibility of terminating the drug | | | | involves passing a direct electrical current |
| administration by simply removing the patch | | | | between two electrodes on the skin surface. |
| from the skin | | | | Phonophoresis uses ultrasonic frequencies to |
| | | | help transfer high molecular weight drugs |
| Improved patient compliance and comfort via | | | | through the skin.A newer and potentially more |
| non-invasive, painless and simple application | | | | promising technology is micro needle-enhanced |
| | | | delivery. These systems use an array of tiny |
| | | | needle-like structures to open pores in the |
| Some of the greatest disadvantages to | | | | stratum corneum and facilitate drug |
| transdermal drug delivery are: | | | | transport. The structures are small enough |
| | | | that they do not reach the nerve endings, so |
| possibility that a local irritation at the | | | | there is no sensation of pain. These systems |
| site of application | | | | have been reported to greatly enhance (up to |
| | | | 100,000 fold) the permeation of |
| Erythema, itching, and local edema can be | | | | macromolecules through skin.Yury Bayarski is |
| caused by the drug, the adhesive, or other | | | | the author of - website, offering patches |
| excipients in the patch formulation | | | | and natural health products. |