Transdermal Drug Delivery Quiz

Study Notes

Transdermal Drug Delivery Systems (TDDS)

A drug must have sufficient lipophilicity to be suitable for transdermal delivery.
TDDS provides stable drug levels, reducing the risk of side effects by minimizing peak-to-trough fluctuations.

Skin Layers

The outermost layer of the skin is called the epidermis.
The epidermis serves as a barrier.
The dermis consists of collagen, elastin fibers, and blood vessels.
The hypodermis, also known as the subcutaneous layer, consists of fat cells, connective tissue, and blood vessels, and provides thermal insulation, shock absorption, and energy storage.

Drug Penetration

There are two main pathways for drug molecules to penetrate the stratum corneum: intercellular and intracellular diffusion.
After penetrating the stratum corneum, drug molecules diffuse to the epidermis and dermis.
Molecular size, lipophilicity, and concentration gradient influence the diffusion of drug molecules through the skin layers.
The ultimate goal of drug molecules penetrating skin layers is absorption into systemic circulation.

Emulsions and Micelles

Emulsifying agents prevent the formation of large globules in emulsions by reducing interfacial tension and forming smaller globules.
Micelle structure is critical in forming emulsions and depends on factors like CMC.
Emulsifying agents play a role in the interfacial film theory by forming a thin layer at the oil-water interface.

Topical Dosage Forms

Ointments are semisolid preparations for external application, providing protective or emollient functions.
Pastes are semisolid forms with 20-50% API, typically made by trituration, with base types including hydrocarbon, water miscible, and water soluble.
Creams have a water content of more than 20%, and their texture, spreadability, and therapeutic properties are determined by their composition.
Lotions are liquid or semi-liquid with low viscosity, typically applied without friction using gauze.
Liniments are liquid or semisolid preparations applied with friction to unbroken skin, and can contain alcohol or oily emulsions.

Microneedle Arrays and Chemical Pleurodesis

Microneedle arrays facilitate drug delivery through microscopic needles that penetrate the stratum corneum.
The purpose of Chemical Pleurodesis is to prevent recurrent pleural effusion, using a talc slurry containing Steritalc and sodium chloride.

Transdermal Patches

A rate-controlling membrane separates the liquid drug formulation from the skin in patches.
Matrix patches dissolve the drug in a gel-based reservoir for controlled release.
A single-layer drug in adhesive has the drug incorporated into one adhesive layer, whereas a multi-layer drug in adhesive has multiple drug-containing layers.
Patch detachment or discomfort can be challenging in ensuring proper patch adhesion in transdermal drug delivery systems.

Description

Test your knowledge on the requirements for a drug to be suitable for transdermal delivery, clinical applications of complex suspensions, pathways for drug molecules to penetrate the stratum corneum, critical factors in forming emulsions, and rate-controlling membranes in drug patches.