Transdermal Drug Delivery Quiz

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.