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What would you say if you had the option to self-administer most medical treatments painlessly?
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-administered healthcare.
Over the past three decades, Strouse has helped numerous medical manufacturers develop innovative skin-adhesive products.
Learning about the types of transdermal patches and their assembly methods will help you explore your product development options.
What Are Transdermal Patches?
Transdermal patches are stick-on adhesives that deliver drugs or solutions 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.
BENEFITS OF USE
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
6 Types of Transdermal Patches
Choosing a transdermal patch type revolves around the most efficient skin permeation and manufacturing feasibility.
Developers design transdermal patches based on how the drug solution is delivered: liquid, gel, or crystalline solid. Similarly, 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 consist of a single layer: a combined drug-adhesive. Once you apply the single-layer patch to the skin, it sticks and deploys the drug.
2. MULTILAYER DRUG IN ADHESIVE PATCH
Multilayer transdermal patches are similar to the single-layer system in that the adhesive layers release the drug, except that BOTH adhesive layers contain the drug.
Multilayer transdermal adhesives typically deliver solutions over a more extended period because the thickness of the layers determines how quickly the drug reaches the skin.
3. RESERVOIR PATCH
Transdermal reservoirs are liquid layers containing the drugs that 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, and any damaged membranes risk a sudden rather than controlled release.
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 delivery rate. The active ingredient is evenly distributed throughout the patch, reducing the 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, such as 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.
It’s also always essential to consider the cleanliness of any medical products. When purchasing materials or using a converter, remember to look for a company with reputable Clean Room capabilities.
How Do Transdermal Patches Work?
Transdermal patches contain a solution and a skin adhesive (often acrylic) that holds the patch in place, allowing the solution to seep into the dermis. Each transdermal patch functions differently depending on its purpose and construction.
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 they can be sold or distributed.
USE-CASE EXAMPLES
One of the most common and recognizable transdermal patches is nicotine patches, which grew popular in the early 2000s as a smoking alternative. Other transdermal examples include:
- Treatments for Vitamin C Deficiency
- CBD delivery for chronic pain
- ADHD (attention deficit hyperactivity disorder) treatments
- Hormone deficiency or replacement
- Nausea relief
TRANSDERMAL PATCH CONSTRUCTION
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. Examples include:
- 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 guards the rest of the patch from the environment
—and a drug reservoir. Different transdermal patches have unique compositions tailored to their purposes, so each patch requires materials with varying strengths and properties.
Some suppliers, such as Solventum, offer specialized materials that protect the drug formulation while controlling its diffusion into the skin.
3 Ways to Manufacture Transdermal Patches
The way you build a transdermal patch depends on the patch type and the drug solution.
1. COAT INITIAL MATERIAL WITH SOLUTION
One way to manufacture transdermal patches is to coat the initial material with the solution BEFORE cutting and processing, enabling a one-pass production process. Still, it isn’t always feasible, given the nature of certain drugs that might limit the amount of handling.
2. OUTSOURCE ADHESIVE PATCH
A converter will cut the shape out of the adhesive, leaving an area to which you can apply the final solution AFTER creating the product's body.
3. OUTSOURCE ADHESIVE PATCH AND BUILD A SECONDARY PART
In certain cases, 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 be attached to the converted adhesive to create your final product.
You’re just about ready to decide which route to take; however, it’s worth finding an expert before you fully commit to your transdermal patch design or materials.
Consult with an Adhesive Patch Manufacturer
When designing a product, it’s easy to underestimate the importance of part manufacturability—a.k.a., ensuring your design and materials lend themselves to manufacturing in the most efficient manner. However, part manufacturability plays a significant role in determining the final price.
Working with a medical converting company will help you achieve your product goals while maintaining an efficient production design. Strouse’s quoting process guides you through the product development process, where our engineers suggest design optimizations to ensure a smoother, simpler, 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.
Partnering with experts like Strouse can streamline the design process when designing a transdermal patch. With over 38 years of experience, Strouse helps ensure that your patch is high-quality and manufacturable.
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
