Basic Components of TDDS work together to ensure efficient, controlled drug delivery through the skin while maximizing therapeutic benefits and minimizing side effects.
Basic Components of Transdermal Drug Delivery Systems (TDDS)
1) Drug (Active Pharmaceutical Ingredient - API)
The therapeutic agent to be delivered.
Key Characteristics:
Suitable molecular weight.
Appropriate lipophilicity.
High potency for effective transdermal delivery.
2) Drug Storage System
Matrix System: Drug uniformly dispersed in a polymer matrix; releases and diffuses over time.
Reservoir System: Drug stored in a liquid reservoir, delivered through a rate-controlling membrane.
3) Backing Layer (Basic Components of TDDS)
Function: Protects the patch from external factors and prevents drug loss.
Material: Impermeable (e.g., polyester, polyethylene) to ensure drug release only through the skin.
4) Rate-Controlling Membrane (Reservoir Systems Only)
Regulates drug release from the reservoir to the skin.
Ensures steady, controlled drug delivery over time.
5) Adhesive Layer
Keeps the patch securely attached to the skin.
Maintains close contact for efficient drug transfer.
Requirements: Hypoallergenic, non-irritating.
6) Permeation Enhancers
Agents that improve skin permeability, facilitating drug transfer through the stratum corneum.
7) Release Liner
A protective cover for the adhesive side, removed before application.
Material: Easily peelable (e.g., polyester).
8) Other Excipients
Purpose: Enhance stability, modify release rate, improve solubility, or preserve the formulation.
Examples include stabilizers, antioxidants, and solvents.