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How Do Transdermal Patches Work?

Posted by: Marina Ruleva on 8/24/20 9:26 AM

Transdermal patches are a well-established method of drug delivery. They provide many benefits to patients, providers, and manufacturers. To develop a successful medicated transdermal patch requires a high level of resources and expertise. The market is well-regulated, and the variables are near-endless. For those interested in bringing a transdermal patch to the market, this article will help you understand the basics.

What Are Transdermal Patches?

Photo of a transdermal patch

Transdermal patches are patches that adhere to the skin as a way to deliver drugs. They provide a specific, predetermined dose of medication which is absorbed through the skin and into the bloodstream. 

Transdermal patches provide a non-invasive and painless method of drug delivery, with the added benefit of providing a constant and consistent therapeutic dosage over a predetermined time period. 

Over recent years, the popularity of and demand for topical drug delivery via adhesive patches has continued to grow, as more and more examples of successful treatments enter the mainstream. 

How Do Transdermal Patches Work?

Transdermal patches deliver drugs topically, where they are absorbed by the skin and into the bloodstream. They provide a consistent delivery of small amounts of a drug into the blood stream over a long period of time. The length of wear time and the amount of drug delivered is different from patch to patch. 

Transdermal patch drug delivery systems include a few basic components: 

  • Backing
  • Drug
  • Membrane
  • Adhesive
  • Liner 

Beyond the basics, things do become more complex, with the introduction of permeation enhancers, stabilizers, and packaging. Transdermal patch development requires discovering the ideal combination of all necessary components into an effective drug delivery system. These different methods of combining them result in different types of transdermal patch designs. Some of the most common designs are matrix, reservoir, multilaminate, and drug-in-adhesive. 

Regardless, all materials and components must be balanced with the drug properties in order to produce an effective drug delivery system.  

A transdermal patch acts as a carrier for a drug, holding it until the point of application. At the point of application, adhesive secures the patch to the skin. This allows the drug access to the skin, where permeation begins. 

Once applied, a patch administers the drug until either the drug is fully absorbed or the patch is removed. 

How to Apply a Patch

The specifics of transdermal patch application are going to differ from system to system. Below, you’ll find a basic outline of how to apply a patch and how to safely remove and discard a patch.

Wash your hands and the area where the patch will be applied

You’ll want to begin the process with clean, dry hands. During manufacturing, patches are packaged into sterile pouches. Washing your hands helps to eliminate any potential contamination. A clean and dry application area will help the patch adhere to your skin. 

Transdermal patch application photo

Hold the patch so that the plastic backing is facing you

This orients the patch so that the adhesive is facing down, which will simplify application. 

Peel off one side of the patch’s backing

Avoid touching the exposed patch, and use the other side of the patch — the side with intact backing — as a handle.

Apply the exposed half of the patch to your skin in the the spot you have chosen 

Still using the liner as a handle — and ensuring the adhesive side of the patch is facing down — apply the exposed portion of the patch to the application area. 

Press the sticky side of the patch against the skin and smooth it down

Apply some light pressure to smooth the patch against the skin to ensure there is good contact. 

Remove the packaging from the other side of the patch 

Fold back the other side of the patch, holding onto the remaining piece of plastic backing and using it to pull the patch across the skin. Apply light pressure to ensure there is good contact across the patch’s full surface area. 

Wash your hands

Complete the application by washing your hands with soap and water.

Removing a transdermal patch

When it’s time to remove your patch, press down on its center to lift the edges away from the skin. Then hold the edge gently and slowly peel the patch away from the skin. 

Before discarding, fold the patch in half (pressing the adhesive sides together) and dispose of it safely. Take care to ensure the discarded patch remains out of the reach of children and pets, as some patches may still contain active drugs.

Use soap and water to wash the skin that was covered with the patch. There may be signs of redness immediately after removal. If the redness does not go away after a short time, contact your doctor, as this could be a reaction to the patch adhesive. 

Types of Transdermal Patch Drug Delivery

Two main subtypes comprise transdermal patch drug delivery systems: passive and active.

Passive vs. Active Systems

Passive transdermal patch drug delivery systems are those that really only on natural diffusion to transfer drug from the patch to the skin and into the body. They provide a consistent diffusion rate, depending upon the characteristics of the skin and the design of the patch.

 

Active transdermal patch drug delivery systems are those that use a specific method to aid in the transfer of drug to the skin and into the body. These methods include chemical enhancers and permeators, physical aids like micro-needles, and low electrical current like iontophoresis.  The amount of diffusion depends on the active method used, the drug characteristics, and the skin.

Transdermal Patch Side Effects

As with any drug delivery system, there exists the potential for side effects, and the possibility of side effects can come from the drug or the patch. 

Take, for instance, oral drugs. This method of drug delivery is capable of causing side effects in some individuals. Ingestion can lead to side effects like upset stomach or nausea, as the drug is absorbed into the bloodstream. 

Transdermal patches, on the other hand, absorb drugs into the bloodstream through the skin. Sometimes developed as an alternative to oral medications, they bypass those common side effects of oral ingestion. Still, a properly applied transdermal patch can cause side effects. 

The most likely side effect of a transdermal patch is irritated skin. Some wearers may have sensitive skin, making them more vulnerable to a reaction. Sensitivity can also result from the drug itself or the dose being too high.

It’s a good practice to talk to your doctor about risks and side effects before using a new drug. Ask about: 

  • Expected side effects
  • Possible side effects
  • Possible drug interactions
  • Drugs or foods to avoid
  • Environmental factors, like sun sensitivity
  • Instructions for applying, wearing, removing, and disposal 

If signs of irritation occur, it’s a good practice to remove the patch and get into contact with the physician or medical professional who prescribed or recommended the treatment. 

Transdermal Patch Adhesives

Adhesives serve a vital role in transdermal patch drug delivery. They keep the patch in contact with the skin, making drug absorption possible. Figuring out the right adhesives is an important part of bringing a new transdermal medication to market. Adhesives for transdermal drug delivery must be skin safe, medical grade, and heat activated. Depending on the style of patch, the adhesive may be combined with the drug in a single formula, as with multilaminate and drug-in-adhesive patches, or kept separate, as with matrix and reservoir style patches. 

Developing a Successful Transdermal Patch 

To develop a successful transdermal patch is a major undertaking. While the benefits can be significant, the process is known to span multiple years. Perhaps the greatest obstacle is underestimating the complexity of formulating a compound for transdermal delivery. 

What is possible with transdermal patch development will depend on the partner you choose. As a full-service CDMO, Tapemark has the staff, experience, equipment, and facilities to bring highly complex transdermal drug delivery systems from concept all the way through manufacturing and shipment. 

Looking to discuss your project with someone well-versed in your specific  focus area? Talk to an Expert

Topics: Transdermal

Marina Ruleva

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