Development

Before these patches go into the market, they have to be carefully studied. One way to study these patches are through the use of Franz Diffusion Cell systems. This system is used to study the effects of temperature on the permeated amount of a specific drug on a certain type of membrane, which in this case would be the membrane that is used in the patches. A Franz Diffusion Cell system is composed of a receptor and a donor cell. In many of these research studies the following procedure is used. The donor cell is set at a specific temperature (the temperature of the body), while the receptor cell is set at different one (temperature of the environment).

Different runs are performed using different temperatures to study the impact of temperature on the release of a certain medicament through a certain type of membrane. Although different concentrations of the medicament are used in this study, they do not affect the amount permeated through the membrane (the process is constant). From Chemical kinetics it concluded that these studies are zero order, since the concentration plays no role in the permeated amount through the membrane.

Some pharmaceuticals must be combined with substances, such as alcohol, within the patch to increase their ability to penetrate the skin in order to be used in a transdermal patch. Others can overwhelm the body if applied in only one place, and are often cut into sections and applied to different parts of the body to avoid this, such as nitroglycerin. Many molecules, however, such as insulin, are too large to pass through the skin.

Popular uses

The highest selling transdermal patch in the United States was the nicotine patch which releases nicotine to help with cessation of tobacco smoking. The first commercially available vapour patch to reduce smoking was approved in Europe in 2007.

Fentanyl, an analgesic for severe pain

Other skin patches administer estrogen for menopause. This also seems to prevent osteoporosis after menopause.

Nitroglycerin patches for angina are available.

Lidocaine patches, marketed as Lidoderm, relieve the peripheral pain of shingles (herpes zoster). It is also now commonly used off-label, for pain from acute injuries and chronic pain, although limited by its requirement to be removed for 12 hours, after 12 hours of use.

Flector (Diclofenac epolamine) patch is an NSAID topical patch for the treatment of acute pain due to minor strains, sprains, and contusions. It is also being used in the treatment of pain and inflammation for chronic conditions benefiting from NSAIDs, including fibromyalgia and arthritis.

Clonidine has also been administered transdermally.

Buprenorphine, marketed as BuTrans, as analgesia for moderate to severe chronic pain

Recent developments expanded their use to the delivery of hormonal contraceptives, antidepressants and even pain killers and stimulants for Attention Deficit Hyperactivity Disorder/ADHD.

Vitamin B1 and Aloe patches are also available as insect repellents

Adverse events

In 2005, the FDA announced that they are 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.

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 removed any medicated patch prior to an MRI scan and replace it with a new patch after the scan is complete.

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

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 in that both adhesive layers are also responsible for the releasing of the drug.One of the layers is for immediate release of the drug and other layer is for control release of drug from the reservoir. The multi-layer system is different however that it adds another layer of drug-in-adhesive, usually separated by a membrane (but not in all cases). This patch also has a temporary liner-layer and a permanent backing.

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. 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.

Vapour Patch

In this type of patch the adhesive layer not only serves to adhere the various layers together but also to release vapour. The vapour patches are new on the market and they release essential oils for up to 6 hours. The vapour patches release essential oils and are used in cases of decongestion mainly. Other vapour patches on the market are controller vapour patches that improve the quality of sleep. Vapour patches that reduce the quantity of cigarettes that one smokes in a month are also available on the market.

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.

See also

Route of administration

Metered dose transdermal spray

References

^ Segal, Marian. “Patches, Pumps and Timed Release: New Ways to Deliver Drugs”. Food and Drug Administration. http://www.fda.gov/bbs/topics/consumer/CON00112.html. Retrieved 2007-02-24. 

^ “FDA approves scopolamine patch to prevent peri-operative nausea”. Food and Drug Administration. 1997-11-10. http://www.fda.gov/bbs/topics/ANSWERS/ANS00834.html. Retrieved 2007-02-12. 

^ Berner B, John VA (February 1994). “Pharmacokinetic characterisation of transdermal delivery systems”. Clinical pharmacokinetics 26 (2): 12134. PMID 8162656. 

^ “FDA ALERT (07/2005): Narcotic Overdose and Death”. Food and Drug Administration. 2005-07-15. http://www.fda.gov/cder/drug/InfoSheets/HCP/fentanylHCP.htm. Retrieved 2007-02-24. 

^ “FDA Public Health Advisory: Risk of Burns during MRI Scans from Transdermal Drug Patches with Metallic Backings”. http://www.fda.gov/cder/drug/advisory/transdermalpatch.htm. Retrieved March 9, 2009. 

Further reading

“Transderm Scp” (PDF). Food and Drug Administration. 1998. http://www.fda.gov/cder/foi/label/2001/17874s27lbl.pdf. Retrieved 2007-02-12. 

External links

The 10th US-Japan Symposium on Drug Delivery Systems

Wikimedia Commons has media related to: Transdermal patches

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Route of administrations / Dosage forms

Oral

Enteral/ digestive tract

Solids

Capsule  Pill  Tablet  Orally disintegrating tablet  Film  OROS (osmotic controlled release capsule)

Liquids

Elixir  Emulsion  Syrup  Suspension  Tincture

Respiratory tract

Inhaler (Metered-dose, Dry powder)  Nebulizer

Circulatory system

Sublingual administration

Eye/ENT

Eye drop  Ear drop  Intranasal

Transdermal

Emulsion (Ointment  Cream  Lotion  Liniment  Gel  Paste  Film)   Medicated shampoo  Transdermal implant  Transdermal patch

Injection/parenteral

Subcutaneous (SC)  Intravenous (IV)  Intramuscular (IM)  Intraosseous  Intraperitoneal (IP)  Intrathecal  Intracavernosal

Vaginal

Pessary (vaginal suppository)  Vaginal ring  Douche  Intrauterine device

Rectal

Suppository  Enema

Categories: Pharmacology | Transdermal patches

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