Transdermal patches and the management of chronic pain

9th June 2007 at 06:54 BST by Dr C.A.Jenner MB BS, FRCA. Permalink.

This article highlights the role of transdermal patches in management of chronic pain.

Transdermal patches and the management of chronic pain

Introduction

A transdermal patch is a modern technique of pain management designed to treat chronic pain and other conditions.

Also known as a skin patch, a transdermal patch is a medicated adhesive patch, which is placed on the skin to deliver regular doses of medication into the bloodstream through the skin.

In the recent years, transdermal patches have proven to be one of the most effective pain management techniques for the treatment of chronic pain.

When administered through this form, the drug is absorbed slowly, requiring 12 to 24 hours to peak, and then giving persistent serum levels for as long as 17 hours after the patch is removed.

Key Components

A transdermal patch is usually made up of five main components, including:

1. Liner – This protects the patch when it is being stored and is removed prior to use.
2. Adhesive – The adhesive helps to adhere the components of the patch together along with adhering the patch to the skin.
3. Drug – The drug solution is the key part of the patch and is in direct contact with the release liner.
4. Membrane – The membrane controls the release of the drug from the reservoir and multi-layer patches.
5. Backing – The backing protects the patch from any adverse effects of the outer environment.

Trends and Usage

Transdermal patches can be used to deliver a vast series of pharmaceuticals. Nicotine patch is the most popular transdermal patch in the United States, used widely to help with cessation of tobacco smoking.

Other conditions in which transdermal patches are commonly used include:

• Motion sickness, with the use of scopolamine
• Menopause, with the use of estrogen
• Osteoporosis
• Angina, with the use of Nitroglycerin patches
• Peripheral pain associated to shingles (herpes zoster), with the use of lidocaine patches

In the recent years, the transdermal patches are also being increasingly used for delivery for hormonal contraceptives, antidepressants and painkillers.

Types of Transdermal Patches

There are four types of transdermal patches that are commonly used for the treatment of chronic pain. Here we've briefly discussed each one of these.

1. Single-layer Drug-in-Adhesive - In this class of transdermal patches, the adhesive layer also contains the drug. Along with adhering the various layers together, the adhesive layer is also responsible for the drug release. The adhesive layer in these patches is surrounded by a temporary liner and a backing.

2. Multi layer Drug-in-Adhesive - In addition to the features of the Single-layer Drug-in Adhesive, this category of transdermal patches has another additional layer of drug-in-adhesive that is normally separated by a membrane.

3. Reservoir – The reservoir transdermal system typically has a separate drug layer. This drug layer is basically a liquid compartment containing a drug solution or suspension separated by the adhesive layer.

4. Matrix – The Matrix system has a drug layer of a semi-solid matrix that contains a drug solution or suspension. The adhesive layer in this patch surrounds the drug layer, partially overlaying it.

Chronic Pain Management – Key Aspects

Transdermal patches have proven to be quite effective in the treatment of chronic pain associated with a series of diseases.

Research shows that the transdermal matrix patch formulation of buprenorphine is quite useful in managing moderate-to severe cancer pain and severe pain unresponsive to nonopioid analgesics.

In general, the transdermal patches are considered to be an effective and well-tolerated treatment method for the treatment of chronic pain caused by malignancy and non-malignant conditions.

As compared with oral opioids, the transdermal patches have a series of advantages. The most important amongst these is the lower incidence and impact of adverse effects, including constipation, nausea, vomiting and daytime drowsiness.

However, another set of research reports indicate towards the adverse effects of the transdermal patches for the management of chronic pain. The potential for serious toxic effects associated with the use transdermal patches is the most crucial factor.

For instance, scopolamine patches that are used to treat motion sickness and prevent nausea and vomiting can result in unilateral and bilateral mydriasis, if the excessive uptake happens through the skin or the patch is rubbed on the eye.

Important Considerations

Before the transdermal patches are administered for the treatment of chronic pain, it is important that the following precautions are observed.

1. Driving and consumption of alcohol should be avoided before and after the patch has been administered.
2. The instructions enclosed with the medicine should be followed carefully.
3. Each transdermal patch should be replaced after 72 hours.
4. Avoid exposure to excessive heat when wearing the patch.
5. The consumption should be reduced gradually, in accordance with proper medical advice.

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