Transdermal patch

A transdermal 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 bloodstream. Often, this promotes healing to an injured area of the body. An advantage of a transdermal drug delivery route over other types of medication delivery such as oral, topical, intravenous, intramuscular, etc. is that the patch provides a controlled release of the medication into the patient, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. The main disadvantage to transdermal delivery systems stems from the fact that the skin is a very effective barrier; as a result, only medications whose molecules are small enough to penetrate the skin can be delivered by this method. A wide variety of pharmaceuticals are now available in transdermal patch form.

Not to be confused with Dermal patch.
A 21mg dose Nicoderm CQ patch applied to the left arm
Contraceptive patch
Clonidine tablets and transdermal patch
A transdermal patch which delivers medication is applied to the skin in a medical setting. The patch is labelled with the time and date of administration as well as the administrator's initials.

The first commercially available prescription patch was approved by the U.S. Food and Drug Administration in December 1979. These patches administered scopolamine for motion sickness.[1][2]

Adverse events
  • In 2005, the FDA announced that they were investigating reports of death and other serious adverse events related to narcotic overdose in patients using Duragesic, the fentanyl transdermal patch for pain control. The Duragesic product label was subsequently updated to add safety information in June 2005.[10]
  • In 2007, Shire and Noven Pharmaceuticals, manufacturers of the Daytrana ADHD patch, announced a voluntary recall of several lots of the patch due to problems with separating the patch from its protective release liner.[11] Since then, no further problems with either the patch or its protective packaging have been reported.
  • In 2008, two manufacturers of the Fentanyl patch, ALZA Pharmaceuticals (a division of major medical manufacturer Johnson & Johnson) and Sandoz, subsequently issued a recall of their versions of the patch due to a manufacturing defect that allowed the gel containing the medication to leak out of its pouch too quickly, which could result in overdose and death.[12] As of March 2009, Sandoz—now manufactured by ALZA—no longer uses gel in its transdermal fentanyl patch; instead, Sandoz-branded fentanyl patches use a matrix/adhesive suspension (where the medication is blended with the adhesive instead of held in a separate pouch with a porous membrane), similar to other fentanyl patch manufacturers such as Mylan and Janssen.[13]
  • In 2009, the FDA announced a public health advisory warning of the risk of burns during MRI scans from transdermal drug patches with metallic backings. Patients should be advised to remove any medicated patch prior to an MRI scan and replace it with a new patch after the scan is complete.[14]
  • In 2009, an article in Europace journal detailed stories of skin burns that occurred with transdermal patches that contain metal (usually as a backing material) caused by shock therapy from external as well as internal cardioverter defibrillators (ICD).[15]

Components

The main components to a transdermal patch are:

  • Liner - Protects the patch during storage. The liner is removed prior to use.
  • Drug - Drug solution in direct contact with release liner
  • Adhesive - Serves to adhere the components of the patch together along with adhering the patch to the skin
  • Membrane - Controls the release of the drug from the reservoir and multi-layer patches
  • Backing - Protects the patch from the outer environment
  • Permeation Enhancer - These are permeation promoters for drugs, which increase delivery of drug.
  • Matrix Filler - Provides bulk to the matrix, and some act as matrix stiffening agents.

Other components include: Stabilizer (anti oxidants), Preservatives etc.

Types
Sample transdermal patches. On left is a 'reservoir' type, on the right a 'Single-layer Drug-in-Adhesive' version. Both contain exactly the same level of the same active ingredient with identical release rates.

There are five main types of transdermal patches.

Single-layer Drug-in-Adhesive

The adhesive layer of this system also contains the drug. In this type of patch the adhesive layer not only serves to adhere the various layers together, along with the entire system to the skin, but is also responsible for the releasing of the drug. The adhesive layer is surrounded by a temporary liner and a backing.

Multi-layer Drug-in-Adhesive

The multi-layer drug-in-adhesive patch is similar to the single-layer system; the multi-layer system is different, however, in that it adds another layer of drug-in-adhesive, usually separated by a membrane (but not in all cases). One of the layers is for immediate release of the drug and other layer is for control release of drug from the reservoir. This patch also has a temporary liner-layer and a permanent backing. The drug release from this depends on membrane permeability and diffusion of drug molecules.

Reservoir

Unlike the single-layer and multi-layer drug-in-adhesive systems, the reservoir transdermal system has a separate drug layer. The drug layer is a liquid compartment containing a drug solution or suspension separated by the adhesive layer. The drug reservoir is totally encapsulated in a shallow compartment molded from a drug-impermeable metallic plastic laminate, with a rate-controlling membrane made of a polymer like vinyl acetate on one surface. This patch is also backed by the backing layer. In this type of system the rate of release is zero order.

Matrix

The matrix system has a drug layer of a semisolid matrix containing a drug solution or suspension. The adhesive layer in this patch surrounds the drug layer, partially overlaying it. Also known as a monolithic device.

Vapour Patch

In a vapour patch, the adhesive layer not only serves to adhere the various layers together but also to release vapour. Vapour patches release essential oils for up to 6 hours and are mainly used for decongestion. Other vapour patches on the market improve quality of sleep or aid in smoking cessation.

Regulatory aspects

A transdermal patch is classified by the U.S. Food and Drug Administration as a combination product, consisting of a medical device combined with a drug or biological product that the device is designed to deliver. Prior to sale in the United States, any transdermal patch product must apply for and receive approval from the Food and Drug Administration, demonstrating safety and efficacy for its intended use.[16]

References
  1. Segal, Marian. "Patches, Pumps and Timed Release: New Ways to Deliver Drugs". Food and Drug Administration. Archived from the original on 2007-02-10. Retrieved 2007-02-24.
  2. "FDA approves scopolamine patch to prevent peri-operative nausea". Food and Drug Administration. 1997-11-10. Archived from the original on 2006-12-19. Retrieved 2007-02-12.
  3. Nachum Z, Shupak A, Gordon CR (2006). "Transdermal scopolamine for prevention of motion sickness : clinical pharmacokinetics and therapeutic applications". Clinical Pharmacokinetics. 45 (6): 543–66. doi:10.2165/00003088-200645060-00001. PMID 16719539.
  4. Berner B, John VA (February 1994). "Pharmacokinetic characterisation of transdermal delivery systems". Clinical Pharmacokinetics. 26 (2): 121–34. doi:10.2165/00003088-199426020-00005. PMID 8162656.
  5. Peck, Peggy (2006-03-01). "FDA Approves First Antidepressant Transdermal Patch". Retrieved 2010-09-28.
  6. Cabray, Matthew (2006-04-12). "Transdermal Patch Approved For Treatment Of ADHD". Retrieved 2010-09-28.
  7. Thirupathi; et al. (2014-05-02). "Preparation and Evaluation of Transdermal Films of Verapamil" (PDF). Retrieved 2018-07-28.
  8. "'Revolutionary' 24-hour slow release 5-HTP transdermal patch, launched in early 2014 in the United Kingdom". 5htppatch.co.uk. Retrieved 2014-06-18.
  9. Peck, Peggy (2007-07-10). "Medical News: FDA Approves Rivastigmine Patch for Alzheimer's Disease". Retrieved 2011-03-10.
  10. "FDA ALERT (07/2005): Narcotic Overdose and Death". Food and Drug Administration. 2005-07-15. Archived from the original on 2007-02-20. Retrieved 2007-02-24.
  11. Megget, Katrina (2007-09-05). "ADHD Transdermal Patches Withdrawn". Retrieved 2010-09-28.
  12. Silverman, Ed (2008-02-12). "J&J and Sandoz Recall Fentanyl Patches". Retrieved 2010-09-28.
  13. As stated on the packaging and labels of Sandoz-branded Fentanyl Transdermal System products, revised March 2009.
  14. "FDA Public Health Advisory: Risk of Burns during MRI Scans from Transdermal Drug Patches with Metallic Backings". Archived from the original on March 7, 2009. Retrieved March 9, 2009.
  15. Brown, MR: "Analgesic patches and defibrillators: a cautionary tale", Europace,2009 Nov;11(11):1552-3
  16. "Combination Products; FAQ". Retrieved April 10, 2012.

Further reading
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