What would you say if you had the option to self-administer painless medical treatments over an extended period?
From people who have trouble swallowing pills to those living in remote areas, transdermal patches are a rapidly growing solution to the demand for accessible, self-administrative healthcare.
Having worked alongside many healthcare companies over the past three decades, Strouse’s engineers are constantly finding new methods for designing and building medical products.
This lesson will help you understand the different types of transdermal patches, the materials used, and how they’re manufactured so you can explore the available options for transdermal product development.
What Are Transdermal Patches?
Transdermal patches are stick-to-skin adhesives embedded with drugs or solutions transferred through the epidermis after prolonged skin contact. An adhesive secures the patch to the skin, allowing the transdermal solution to gradually absorb through the skin cells, reach the dermis, and enter the bloodstream.
One of the most common and recognizable transdermal patches is nicotine patches, which were popularized in the early 2000s as a smoking alternative. Other types include treatments for Vitamin C deficiency, CBD delivery, ADHD treatments, hormone deficiency or replacement, nausea relief, and even fragrance delivery or insect-repelling transdermal patches.
What is the Purpose of a Transdermal Patch?
Transdermal patches are an alternative method of delivering drugs, nutrients, or other solutions. Rather than taking a pill or getting a shot, medications are increasingly adapted for transdermal applications. The benefits of using transdermal patches include:
- Convenience (relatively easy to apply)
- Consistency (predictable and timely doses)
- Smoother dosing
- Avoiding digestive side effects
- Improving patient experience
What Are the Different Types of Transdermal Patches?
Different transdermal patches are designed based on how the drug solution deploys. Transdermal solutions can be liquid, gel, or crystallized solid, and choosing a type of transdermal patch revolves around the most efficient skin transmission and manufacturing feasibility.
The type of patch you build will depend on the delivery requirements of your drug solution and the nature of your production set-up.
1. SINGLE-LAYER DRUG IN ADHESIVE PATCH
Single-layer transdermal patches are comprised of one layer: combined drug and adhesive. A single-layer patch is applied to the skin, where it sticks and deploys the drug.
2. MULTILAYER DRUG IN ADHESIVE PATCH
Multilayer transdermal patches are similar to the single-layer system in that adhesive layers release the drug, except BOTH adhesive layers contain drugs. Typically, multilayer transdermal adhesives deploy solutions over a longer period of time because the width of the layers determines how quickly the drug reaches the skin.
3. RESERVOIR PATCH
Transdermal reservoirs are liquid layers containing the drugs which are gradually delivered to the skin through a rate-controlling membrane. These reservoir patches allow for more controlled delivery rates, but the initial drug release can be a slight burst. In addition, if the membrane is damaged, there is a risk of sudden release into the skin.
4. MATRIX PATCH
A transdermal matrix patch includes an adhesive polymer matrix containing the drug, which is gradually released into the skin. Unlike the rate-controlling membrane in a reservoir patch, the formulation of its drug and polymer matrix dictates the rate of drug delivery. The active ingredient is distributed evenly throughout the patch, so there is less risk of accidental release.
5. MICRONEEDLE PATCH
Microneedle patches are transdermal patches with microscopic needles that penetrate the epidermis deep enough to help drugs enter the bloodstream. Despite the needles, they are painless and can deliver drugs more effectively for faster absorption
Needles are typically preloaded with drug solutions, assembled separately, and then placed onto the adhesive patch. For example, Strouse creates adhesive patches for medical devices like microneedles but doesn't manufacture the needles. Instead, manufacturers often use automated systems to attach the preloaded needles to the patch.
6. IONTOPHORESIS PATCH
Iontophoresis patches are medical devices that use small electrical currents to deliver charged substances to the skin. This substance is often applied directly to a designated spot on the patch before use and can consist of tap water for milder uses.
What Are Transdermal Patches Made of?
Material manufacturers often use stick-to-skin adhesives or bonding components to create transdermal patches. Each layer of a transdermal patch might consist of a different material. For instance, the primary components are:
- Liner: Protects the adhesive, removed before application
- Drug/solution: Can be mixed with the adhesive or remain on its own, often in direct contact with the liner
- Adhesive: Joins together the patch itself while simultaneously adhering the device to the skin
- Membrane: Dictates the rate of transmission in multilayer and reservoir transdermal patches
- Backing: The protective outer layer guarding the rest of the patch from the environment
Different transdermal patches have unique compositions to match their purposes, so different patches will require materials of varying strengths and abilities. Some suppliers, such as Solventum, offer specialized materials that protect the drug formulation while controlling its diffusion into the skin.
It’s also always essential to consider the cleanliness of any medical products. When purchasing materials or using a converter, remember that you’ll want to search for a company with reputable Clean Room capabilities.
The U.S. Food and Drug Administration (FDA) classifies transdermal patches as “combination products” because they are medical devices merged with a drug or biological product. Therefore, they require safety approval before being sold or distributed.
How Are Transdermal Patches Manufactured?
Transdermal patches are manufactured in various ways depending on the patch type and the drug solution.
One way to manufacture transdermal patches is to coat the initial material with the solution BEFORE cutting and processing it.
This potentially allows a one-pass production process, but it isn’t always feasible, given the nature of certain drugs that might limit the amount of handling.
Another transdermal patch manufacturing method is outsourcing the adhesive patch from a flexible material converter.
The converter cuts out the shape of the adhesive and leaves an area to which the final solution can be applied AFTER the body of the product is created.
Lastly, it’s possible to acquire the adhesive patch from a converter while manufacturing your own secondary part loaded with the transdermal solution.
This secondary part can then be attached to the converted adhesive to create your final product.
With these options in mind, you’re just about ready to decide which route to take when building your transdermal patch design. However, it’s worth seeking out an expert before you fully commit to your design or materials.
When designing a product, it’s easy to underestimate the importance of part manufacturability—a.k.a. making sure your design and materials lend themselves to manufacturing in the most efficient manner. However, part manufacturability plays a major role in determining the final price.
When designing a transdermal patch, partnering with experts like Strouse can streamline the process. With over 30 years of experience, Strouse helps ensure that your patch is high-quality and manufacturable.
Working with an adhesive converter will allow you to achieve your product goals while retaining an efficient production design. For example, Strouse’s quoting process brings you through the product development process, where our engineers will suggest design optimizations to ensure a smoother, less complicated, and more affordable manufacturing process.
Your final result shouldn’t depend solely on your manufacturing knowledge. Instead, consider reaching out to find a trusted partner who will help you succeed.
To gain more insight into skin adhesives and transdermal applications, visit Strouse’s Learning Center, where you can find all of our educational materials.
Originally published: May 23, 2023
