Medical Patches: The Ultimate Skin Adhesive Wearables And How They Are Made

Medical patches are wearable medical devices that continuously deliver a measured amount of medication. This type of transdermal medicine delivery is growing in popularity.

Physicians like them because they ensure patients consistently gets the amount of medication they need every day. Patients like them because it means they can receive their medication passively and they don’t have the stress of trying to remember when and how much of the medication they need to take.

These medical patches are revolutionizing the delivery of medication and can help to improve treatment outcomes.

How They Are Produced

Manufacturing transdermal medical patches requires the use of precision equipment that is able to meet tight tolerances and adhere to strict regulations. Choosing the right materials is essential. The primary components used to produce transdermal patches include:

  1. Drug Solution
  2. Liner
  3. Adhesive
  4. Membrane
  5. Backing
  6. Permeation Enhancer
  7. Matrix Filler
  8. Stabilizers
  9. Preservatives

The Role Each Component Plays

The most important component in any medicinal patch is the drug solution. This is what helps the patient to heal when it makes direct contact with the skin. The right liner is essential because it is what protects the medical patch during storage.

It is removed just prior to the patch being used. Adhesives hold together the components of which the patch is made and enables the patch to adhere to the skin. The membrane controls the drug’s release from the reservoir in which it is held. The patch’s backing protects it from the outer environment.

Permeation enhancers are used to increase the delivery of the drugs prescribed by the physician. The patches also contain matrix fillers that are used as stiffening agents for the drug matrix. Stabilizers containing antioxidants is another important element. So are the preservatives which help to increase the shelf-life of the medical patches.

How The Patches Work

Medicinal transdermal patches are designed to adhere to the skin of the patient. Throughout the day the medication they contain is gradually absorbed through the skin and a specific size dose makes its way through the layers of the skin and into the bloodstream.

It’s a painless, non-invasive, way for a constant therapeutic dose of medication to be administered to a patient. The medicinal patches are designed to work for a set time period before being removed.

For both patients and caregivers they are a simple, useful, tool for ensuring the right amount of medicine is consistently delivered at the appropriate time.

Drug Properties Dictate Patch Design

The active ingredient and other properties of the drug being used dictates some elements of the design of these wearable medical devices. Some properties and characteristics of the drug to be administered that must be considered when creating the transdermal patches include:

  1. Molecular Weight
  2. Lipophilicity
  3. Dosage Form
  4. Salt
  5. Length Of Time Worn
  6. Active Ingredient Melting Point

How These Properties Impact Patch Design

The molecular weight and the drug molecules’ size must be taken into consideration. Only small molecules of less than 500 Daltons are able to penetrate the skin. The drug’s lipophilicity also determines how readily it will be absorbed into the oils of the body.

The form in which the dosage of the drug will be administered is also important. The speed at which the skin can absorb the drugs is also determined by the drug’s salt form. The size of the dosage the patient must receive is a decisive factor in the length of time the transdermal patch will be worn.

The Drug’s Amount And Melting Point

Only a reasonable amount of any drug can be put into the patch and it can only be designed to be worn for a realistic length of time. The drug’s active ingredient’s melting point must also be considered. It must be suitable to be placed on the skin without irritating it excessively and prohibiting the patch from being manufactured.

Four Transdermal Patch Designs

Typically, transdermal patches are designed in one of four ways.  They are:

  1. Matrix
  2. Classic Reservoir
  3. Polymer Reservoir
  4. Multilaminate Solid-State Reservoir

The drug’s properties, dosage level, as well as the amount of time required in order for it to be properly administered, influences the design of the patch that is used. The matrix puts the active ingredient into the patch.

Commonly referred to as the drug-in adhesive, manufacturers use this method most often. When the classic reservoir method is used, the active ingredient is encased within it. This method employ a rate-controlling membrane called a blister pouch on one side with an impervious backing placed on the other side.

The polymer reservoir is a semi-solid drug which contains the polymer matrix. An adhesive ring placed around the matrix helps to create direct contact between it and the skin and holds it firmly in place.

A multilaminate solid-state reservoir is used when the medical patch has to deliver two drugs that have different release times.  It usually releases a bolus dose first, followed by a maintenance dose.

Materials and Equipment

Choosing the right materials for the transdermal patch is very important. The liner, membrane, backing and overlaminate tapes to be used must be in balance with the patch design that is chosen as well as the properties of the drug to be administered.

The equipment to be used to manufacture the medical patch must also be considered when deciding on the materials to be used. If the materials the manufacturer uses in the patch must be processed under low tension, it requires a specific type of manufacturing equipment.

The materials and the equipment must be compatible to ensure a smooth commercialization process.

Other Important Production Factors

There are several other important production factors to which transdermal medical patch manufacturers must pay attention. They must make sure to provide the FDA with the requisite Drug Master File.

This confidential document must contain the patch’s manufacturing details. The FDA will access the drug master file and determine whether to grant approval for the medical patch to be produced.

The manufacturer must also verify the volume of the drug that will be used in the patch. This dictates the materials and equipment to be used.

Monitor The Updated FDA Guidelines

Transdermal medical patch manufacturers must pay close attention to the evolving FDA guidelines related to the production of the patches. That can determine the design to be used and can lead to new innovations in the way the patches are produced.

One set of evolving FDA regulations being considered is related to the patch itself and the liner. Manufacturers may be required to use an opaque patch with a writable backing and a translucent liner. This will enable medical providers and patients to write the date on which they applied the patch on the backing.

A Complicated Development Process

The process for developing transdermal patches is remarkably complicated. Plus, there are a number of variables to which it can be subjected. Throughout the process, manufacturers must work closely with the vendors that supply the materials and the equipment with which they work.

Transdermal medical patch producers must align themselves with partners that have a clear understanding of the complexities of dealing with both the product and the manufacturing process.

The Customer’s Responsibility

Transdermal medical patches can potentially revolutionize medicine delivery. However, it’s ultimately the responsibility of the customer to determine if the components and design of the wearable medical devices is suitable for the drugs intended use and meets the requisite safety and toxicity standards.

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