Transdermal Drug Delivery Systems (TDDS) Overview

Practice questions covering the definition, advantages, disadvantages, components, and types of transdermal drug delivery systems.

How is a transdermal drug delivery system (TDDS) defined?

A delivery device which, upon application on a suitable skin surface, delivers drug into the systemic circulation at a constant rate and adequate concentration to ensure therapeutic efficacy.

In contrast to transdermal patches, what is the journey of a medicine in pill form?

It must go through the digestive system, be absorbed into the blood, and pass through the liver (where the liver may eliminate it) before circulating to the rest of the body.

What effect do transdermal patches avoid by delivering drugs straight through the skin?

They avoid the first pass effect.

How do transdermal patches improve patient compliance compared to other dosage forms?

By providing extended therapy with a single application, reducing the need for frequent dose administration.

What are two physiological benefits of using a patch for drugs with short biological half-lives?

It allows for continued drug administration and maintains a steady permeation of drug across the skin for consistent serum drug levels.

What types of drug structures typically permeate the skin too slowly for TDDS?

Hydrophilic structures.

Why must drug molecules used in transdermal patches be potent?

Because patch size limits the amount of drug that can be delivered, making them unsuitable for high drug doses.

List the physicochemical properties of the penetrant that affect transdermal delivery.

Molecular size, partition coefficient, solubility, ionization, penetrant concentration, and diffusion coefficient.

Which physiological properties can influence the delivery of drugs through the skin?

Site of application, skin temperature, skin condition, blood supply, skin metabolism, hydration state of stratum corneum, and biological factors such as age, sex, and race.

What are the ideal drug selection criteria for TDDS regarding metabolism and molecular weight?

Extensive metabolism and low molecular weight.

What are Pressure sensitive adhesives (PSAs) and their requirements?

They affix the TDS firmly to the skin with finger pressure, must be tacky, exert a strong holding face, and should be removable without leaving a residue.

Name three commercially used Pressure sensitive adhesives (PSAs).

Polyacrylate, polyisobutylene, and silicones.

What is the purpose of backing laminates in a transdermal patch?

To protect the skin from the outer environment and promote better adhesion and skin hydration via a low water vapour transmission rate.

What materials are commonly used for the base layer and release coating of a release liner?

The base layer is occlusive or non-occlusive, and the coating layer is made of silicon or teflon.

Identify common solvents and plasticizers used as excipients in TDDS.

Solvents include chloroform, methanol, and acetone; plasticizers include triethyl citrate, PEG, and propylene glycol.

Describe the Single layer Drug in Adhesive system.

In this system, the adhesive layer contains the drug and is responsible for both adhering the system to the skin and releasing the drug.

What components make up a Drug Reservoir transdermal system?

An impermeable backing, the drug reservoir, a rate controlling membrane, and an adhesive.

Name five types of transdermal patches available today.

Nicotine patch, patch for severe pain, antihypertensive patch, Vitamin B12 patch, and antidepressant patch.