Have you seen anyone using a nicotine patch? It is this round-shaped patch that looks like a big band-aid that is attached to the biceps or in some part of the hand. The patch contains nicotine and goes through the pores of the skin and instead of inhaling it directly, it goes through a different path so that you can quit smoking after a few days. A transdermal patch is almost the same. However, instead of nicotine, these patches have drugs in them. There are hundreds of patients who are not able to have medicines orally. Moreover, there are several drugs that cannot be injected in the body too. So, the best option is to use transdermal patches so that the drug goes directly into the body without harassing the patient. It is a non-invasive and painless way of providing medication and the dosage is controlled and prescribed by the doctor.
There are many ways in which a transdermal patch can be made. Different patches have different properties and the concentration of the drug is not the same in every patch. That is why the layers in the patch are different. Here is a generic way in which a transdermal patch is made that most of the manufacturers follow:
Step 1 – Focusing on the drug properties
The patch that will be designed will have certain drugs in it. It is important that the properties of that drug are checked before it is used in the patch. The first factor that is considered is the molecular weight of the drug. Ideally, it should be less than 500 Daltons. Also, the lipophilicity is taken into consideration so that the makers can understand the time in which the drug will start to reach the desired areas of the body. The duration of the patch, dosage form, and melting point of the drug, and salt content are all critical points that are checked thoroughly before the patch is even designed.
Step 2 – Choosing the patch design
Transdermal patches are designed according to the dosage level, the time taken for the drug to react, and the properties of the drug. Generally, there are four ways in which the design of the patch can be decided. They are as follows:
- Classic reservoir – these will look like a blister pouch. The patch will have active ingredients present in them with rate-controlling membrane and impervious backing on either side. The patch will be slightly thicker than the other varieties.
- Multilaminate Solid-State Reservoir – these patches have the ability to deliver two different drugs at different times. They are the most advanced of all the transdermal patches. These patches will have a bolus dose to start with and will then move on to a maintenance dose. They also have a lengthier time span than the other patches.
- Matrix – these are the most common transdermal patches and are easy to design. There will be an active ingredient that is used directly on the patch. The ends are sealed together and they are ready to be used by the patient. They generally last for a couple of days or even less.
- Polymer Reservoir – these patches will contain a semi-solid drug that consists of a polymer matrix. The patch is designed in such a way so that it will touch the skin of the patient. There is an adhesive ring that holds the patch together. The drug that is used inside is normally present in a concentrated form so that the body can react to it quickly.
Step 3 – Covering the transdermal patch
Now that you know the ingredients that are used and the various designs of the transdermal patch, it is time to close the patch so that it is ready for use. Different patches will require different materials to close the patch but it is important to choose the appropriate materials. Some of the common items that will be required are overlaminate tapes, membrane, backing, and the liner. However, the use of these items will be decided on the type of drug and the amount of drug that is used inside the patch.
Testing and quality control
Every transdermal patch has to go through several quality checks before they are finally used by the patient. In addition to the quality control, the patches will have to go through two sets of testing: the in-process testing and the other is finished-product testing.
In-product testing, as the name suggests, is the testing of the materials that are used inside the patch. It checks the materials that are affected during the manufacturing process. One of the reasons why there are several levels of this testing is to make sure that the right balance is achieved inside the patch. The blending process is checked thoroughly to see if it has a homogenous mix and the quantifying and measuring of the adhesion that was used during the manufacturing of the patches.
Finished-product testing is slightly different. It does not involve the testing of the manufacturing process. Rather, it focuses on the performance and physical characteristics of the patch. Some of the common finished-product testing that is done before giving the green signal is the adhesion and tack testing. This will help to understand the duration for which the patch will stay on the skin of the patient. If the patch is made to last for 7 days, then the adhesion level has to be more and vice-versa. So, the manufacturers have to make sure that the drugs that are used inside and the backing that is used has a good balance with the adhesion level. This will determine if the patch will pass the adhesion and tacking test.
The making of a transdermal patch from http://rdmedicalproducts.com is more like putting some medicine in a cotton ball and sealing it with a band-aid on your arm. Although the concept is the same, the manufacturing process is way different and there are so many things that have to be taken into consideration while the transdermal patch is made.