transdermal delivery

Question 1

What are the main layers of the skin relevant to transdermal drug delivery?

Answer 1

The skin consists of the epidermis, dermis, and subcutaneous tissue. The outermost layer, the stratum corneum, is a dense, almost impermeable barrier.

Question 2

What is the primary objective of transdermal drug delivery?

Answer 2

To deliver drugs directly to the bloodstream, bypassing the GI tract and avoiding first-pass metabolism in the liver.

Question 3

What are the advantages of transdermal drug delivery?

Answer 3

1. It provides steady-state drug delivery, avoids GI degradation
2. bypasses first-pass metabolism.
3. continuous drug delivery is desirable.

Question 4

What are some limitations of transdermal drug delivery?

Answer 4

1. Only suitable for potent, lipophilic drugs
2. potential for skin irritation
3. variable delivery due to skin’s barrier properties.

Question 5

What are the main routes of penetration for transdermal drugs?

Answer 5

Transdermal drugs penetrate through the stratum corneum (transepidermal route) or via appendages like hair follicles

Question 6

Name factors that affect skin permeability.

Answer 6

1. Body site
2. age
3. skin condition
4. hydration level
5. drug formulation all influence permeability.
6. metabolism

Question 7

What formulation factors can increase drug absorption through the skin?

Answer 7

Drug solubility, pH, drug concentration, contact time, surface area, hydration and use of penetration enhancers.

Question 8

Name some methods to enhance transdermal drug penetration.

Answer 8

Hydration, ultrasound, microneedles, electroporation, high-velocity particle injection, and chemical penetration enhancers.

Question 9

What are transdermal patches used for?

Answer 9

They provide controlled release of drugs for systemic therapy, commonly used for conditions like pain management and hormone replacement.

Question 10

what are the two types of transdermal systems? and explain the structure of them.

Answer 10

1. membrane systems. (top is impermeable backing, then drug reservoir, then rate limiting membrane, adhesive layer at bottom.)
2. gradient corneum. (top is impermeable backing, multiple drug reservoir gradient layers, then adhesive.)

Question 11

Give examples of drugs delivered by transdermal patches.

Answer 11

glycerol trinitrate for angina, estradiol for menopause, clonidine for hypertension, and fentanyl for pain.

Question 12

How does iontophoresis enhance drug delivery through the skin?

Answer 12

Iontophoresis uses an electric field to increase penetration of ionic, neutral, or polar molecules across the skin.

Question 13

How does iontophoresis transport charged molecules?

Answer 13

Transport is driven by electrical repulsion from a drug-containing electrode and, for neutral molecules, by electro-osmosis.