Medicine Storehouse on Skin 1: Analysis of Transdermal Patch

In the long game between humans and diseases, every innovation in drug delivery technology is like a key to unlock the mysteries of life. Transdermal patches, an innovative drug delivery product, eliminate the pain of needle tips and gastrointestinal tossing, allowing drugs to pass through the natural barrier of the skin and reach the lesion with precise controlled release , bringing patients a new medication experience.

1. The revolutionary significance of transdermal drug delivery

(1). Definition of Transdermal Drug Delivery System (TDDS)

Transdermal Drug Delivery System (TDDS) is an innovative technology for delivering drugs through the skin surface. Its core principle is to continuously penetrate the drug into the deep layer of the epidermis or dermis at a controllable rate, and finally enter the systemic circulation to exert systemic therapeutic effects, and can also act on local target tissues. It is the third largest drug delivery system after oral and injection, and is widely used in the pharmaceutical and beauty industries.

(2)Core Advantages

The skin is the largest organ in the human body. When drugs are administered through the skin, drug absorption is not affected by factors such as PH, food, and transit time in the digestive tract; the first-pass effect in the liver is avoided; and adverse reactions caused by excessive blood drug concentrations due to rapid absorption are overcome.

(3)Transdermal patch: one of the specific product forms

A transdermal patch is a patch that is attached to the skin and contains drugs. It can deliver a specific dose of drugs into the blood through the skin, allowing the drugs in the patch to be absorbed by the body within a set time. Compared with traditional solid preparations and intramuscular injections, transdermal patches have higher compliance, especially for the elderly and children. It only needs to be attached to the skin, which is painless and non-invasive , and is a new direction for technological innovation in the future medical field. Transdermal patches are usually composed of multiple layers, each of which has its specific function:

Backing layer: protects the drug in the patch from the influence of the external environment;

Drug layer: carries drugs;

Controlled release layer: controls the release rate of the drug, allowing the drug to slowly release its medicinal properties within a designed period of time;

Adhesive layer: allows the patch to stick to the skin and not fall off;

Release film: used to protect the adhesive layer and drug preparation, and needs to be removed before using the patch.

2.Analysis of the core technology of transdermal patches: classification

• Reservoir system

This type of drug release system uses a multilayer composite structure of a backing layer, a drug reservoir layer, a controlled release membrane, and an adhesive layer. The drug reservoir is located between the backing layer and the controlled release membrane, and its form can be a solution, suspension, gel, or solid polymer dispersion system. The microporous controlled release membrane is used to precisely control the drug release rate.

• Matrix system

In this type, the drug is evenly dispersed in a hydrophilic or lipophilic polymer matrix. The drug diffuses through the matrix at a rate determined by the solubility of the matrix.

• Drug-in adhesive system

The simplest membrane permeation control system. The adhesive layer in this type contains the drug and is used to bind the layers together. The drug mixture is sandwiched between the liner and the backing to form a "sandwich" structure without a separate reservoir/matrix.

• Micro-reservoir system

This type is a combination of reservoir and matrix. The drug is encapsulated in tiny reservoir units, which are made of hydrophilic materials to form a structure similar to "microcapsules". The reservoir units are evenly dispersed in the skeleton formed by the polymer, and the drug slowly seeps out from the outer membrane of the micro-reservoir and diffuses into the skin through the adhesive layer.

3.The pros and cons of transdermal patches: the duality of science and business

1. Advantages of transdermal patches

Transdermal patches have many advantages that make them popular in the pharmaceutical field.

• Improved bioavailability

The efficacy of traditional oral tablets and capsules will decrease by 10%-80% after being metabolized by the liver. Transdermal patches deliver drugs through the skin and directly enter the bloodstream, avoiding the first-pass effect, allowing the drug to exert its maximum efficacy and improving bioavailability.

• Non-invasive, high patient compliance

Most oral medicines on the market have a bitter taste, which can cause patients to have psychological resistance to taking medicine; injections can cause physical pain to patients. Compared with the first two, transdermal patches only need to be pasted on the skin to work, and are more acceptable to patients.

• Precise dosage

Traditional preparations and plasters have large errors in dosage, while the error of drug loading per unit area of transdermal patches is ≤±5%, and the drug delivery is precise, making it suitable for children, the elderly, and pets of different sizes.

• Long-term protection

Traditional oral or injectable drugs need to be taken multiple times a day at a fixed point and in a fixed amount, while transdermal patches release the drug properties at a constant rate within a certain period of time, accurately controlling the amount of drug released per unit time . The efficacy can last from 24 hours to a week, without the need to frequently change the drug, maintaining a stable blood drug concentration, thereby reducing the instability of efficacy or side effects caused by fluctuations in blood drug concentration.

• One formula, multiple doses

Traditional solid preparations require different formulations for different dosages, but transdermal patches can increase or decrease the dosage by changing the drug coating area. Only an accurate initial formula is needed to produce products of different dosages to better serve patients of different ages and with different degrees of illness.

• Meeting the medication needs of special groups

For the elderly, patients with dysphagia and children who are unwilling to take medicine, taking solid preparations is difficult and may even cause suffocation. Transdermal administration is more acceptable and convenient, and can also be used as the preferred route of administration for comatose and nauseous patients.

• Lightweight and portable, highly concealed

Transdermal patch products are small in size and light in weight, extremely portable, and can be used on non-exposed skin to protect personal privacy.

• Targeted drug delivery

Transdermal patches can be applied directly to the affected area to achieve targeted drug delivery. This method is very effective in treating localized symptoms such as pain, inflammation and skin diseases.

2. Disadvantages of transdermal patches

• Medication withdrawal

In daily life, friction from clothing and water contact may cause the drug film to fall off accidentally, thus interrupting the treatment.

• Allergy symptoms

Substances in the drug layer or adhesive layer may irritate the skin and cause rash, redness, swelling, or irritant dermatitis.

• Medication restrictions

The impermeability of the skin is a natural restriction on the entry of drugs, so only potent drugs and lipophilic drugs are suitable for making transdermal patches. Drugs with hydrophilic structures need to be modified into a suitable form, otherwise they cannot enter the systemic circulation. In addition, some drugs that are irritating and allergic to the skin are not suitable for designing into transdermal patches.

• Slow effect

It is difficult for drug ingredients to pass through the stratum corneum of the skin, resulting in a slow onset of effect. Generally, it takes a period of time for the drug to take effect , and the effective concentration may not be reached.

• Treatment effects vary widely

The skin's barrier function varies in different parts of the same person, between different people, and with age , so the effects of the same transdermal patch product may vary greatly.

• Wearing discomfort

Patches can be uncomfortable to apply because the adhesive may not adhere well to all skin types. Transdermal patches are more noticeable than oral medications and may cause discomfort to patients.

It can be seen that as an innovative product, transdermal patches have both advantages and disadvantages. But overall, the emergence of transdermal patches has brought many conveniences to medication, and its disadvantages can also be solved more perfectly with the help of scientific and technological forces and technological innovation in future development. Disadvantages do not entirely represent product defects, but more importantly, they make us realize that there is still room for improvement. If you have any questions about transdermal patch production technology, please consult us -Aligned, focusing on the pharmaceutical industry, providing you with a one-stop solution.