The key difference between transdermal and intradermal is that transdermal is a type of drug delivery route where drugs are directly applied onto the intact and healthy skin, whereas intradermal is a type of drug delivery route where drugs are directly injected into the outer layer of the dermis underneath the upper skin layer.
The way drugs are administered is typically categorized according to where they are applied in the body, including options like oral, subcutaneous, and intravenous routes. These administration routes encompass various methods, including enteral (through the digestive system), oral, sublingual (under the tongue), buccal (inside the cheek), rectal, intravenous, intramuscular, subcutaneous, transdermal (through the skin), and intradermal routes.
CONTENTS
1. Overview and Key Difference
2. What is Transdermal
3. What is Intradermal
4. Similarities – Transdermal and Intradermal
5. Transdermal vs Intradermal in Tabular Form
6. Summary – Transdermal vs Intradermal
What is Transdermal?
Transdermal is a route of drug administration where active drugs are delivered across the skin for systemic distribution. In this route, drugs are directly applied to the intact skin. It is a painless method of delivering drugs. In this method, the drug initially penetrates the stratum corneum of the skin’s epidermis and then passes through the deeper epidermis and dermis to systematic circulation. There are only limited drugs that meet the criteria required to be able to bypass the skin, as in the transdermal route. To be administrated in the transdermal route, the drug should have the following criteria: a low molecular weight, the ability to pass through the epidermis, the ability to be absorbed by the blood vessels and enter the systematic circulation, and the ability to be chemically and physically stable.
Figure 01: Transdermal
The transdermal drug delivery route offers significant advantages by bypassing the liver’s first-pass metabolism, thereby protecting drugs from potential degradation. It also reduces the risk of gastrointestinal system damage compared to the oral route and enhances the likelihood of consistent patient compliance and usage. However, there are certain adverse effects in transdermal drug delivery, like skin reactions (pruritis, burns, and redness of the surrounding area) and allergic reactions.
What is Intradermal?
Intradermal is a route of drug administration where active drugs are injected into the dermis’s outer layer underneath the upper skin layer. Intradermal injections are shallow or superficial injections that inject substances into the dermis, located between the epidermis and the hypodermis of the skin.
Figure 02: Intradermal
Intradermal injections are particularly utilized in fields such as vaccination, immunology, and innovative cancer therapies due to their ability to achieve faster systemic uptake compared to subcutaneous injections. However, the intradermal route may cause certain adverse effects such as flushing or redness of the skin, itching skin, small red or purple spots on the skin, and unusually warm skin.
What are the Similarities Between Transdermal and Intradermal?
- Transdermal and intradermal are two drug delivery routes that use the skin as the location to deliver the drug.
- These drug delivery routes are cost-effective.
- Both drug delivery routes have significant advantages over other methods.
- They also have certain adverse effects.
What is the Difference Between Transdermal and Intradermal?
In the transdermal drug delivery route, drugs are directly applied onto the intact and healthy skin, while in the intradermal drug delivery route, drugs are directly injected into the outer layer of the dermis underneath the upper skin layer. Thus, this is the key difference between transdermal and intradermal. Furthermore, transdermal is a painless drug delivery route, while intradermal is a painful drug delivery route.
The infographic below presents the differences between transdermal and intradermal in tabular form for side-by-side comparison.
Summary – Transdermal vs. Intradermal
In pharmacology, the route of administration is the path by which a drug or other substance is taken into the body. The route of administration can be classified based on the location at which the drug is applied, such as oral, intravenous, enteral, topical, parenteral, etc. Transdermal and intradermal are two drug delivery routes that use the skin as the location to deliver the drug. Transdermal is a type of drug delivery route where drugs are directly applied onto the intact and healthy skin, whereas intradermal is a type of drug delivery route where drugs are directly injected into the outer layer of the dermis underneath the upper skin layer. So, this summarizes the difference between transdermal and intradermal.
Reference:
1. “Transdermal – An Overview.” ScienceDirect.
2. Anderson, Renée, et al. “7.3 Intradermal Injections.” Clinical Procedures for Safer Patient Care, Thompson Rivers University.
Image Courtesy:
1. “A generic fentanyl transdermal patch, with a release rate of 12mcg per hour, applied to the skin” By DanielTahar – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Intradermal, influenza, virus, vaccine, male, clinic, patient, patients, shoulder” (CC0) via Pixino