Lecture 13: Transdermal drug delivery in CV Flashcards
What are the three layers of the skin?
- Epidermis
- Dermis
- Subcutaneous tissue
What cells are found in the epidermis?
- Keratinocytes
- Melanocytes
- Langerhans cells
What is found in the dermis layer? (5)
- Sweat duct
- Sebaceous gland
- Sweat gland
- Arrector pili
- Hair follicle
What is found in the subcateneous tissue?
- Blood vessels
- Fat lobules
What is the principle barrier of the skin?
Stratum corneum
What is the largest organ of the body?
Skin
What is the size of the skin?
1.8m2
What is the pH of the skin surface
pH 5
What are the routes transdermal drugs use?
- Shunt route
- Trancellular route
- Intracellular route
What are the physiochemical properties affecting transdermal drug delivery?
- Ability to cross lipid bilayer, especially corneocytes
- Diffusion through aqueous environment, epidermis
What are the general properties required for transdermal drug delivery?
- Molecular weight < 500
- LogP in the range of 1 to 4
- Maximum daily dose of 10mg/ day
Give examples of drugs delivered transdermally (3)
- Estradiol
- Fentanyl
- Nicotine
What is ficks law of diffusion?
Flux of drug molecules from high to low concentration
What are the five principles of skin permeation?
- Selection of suitable drug molecule
- Release of drug from formulation
- Use thermodynamics
- Alcohol can help - partitions into skin, sets up a transient reservoir for drug to partition into, drives maximum thermodynamic activity
- Occlusion increases delivery of most drugs - Hydrates skin by blocking transdermal water loss, EMLA cream applied under occlusive dressing
How is skin permeation measured?
Using franz diffusion cell
What are the advantages of transdermal patches?
- Avoids the harsh environment of the GI tract
- Drug reaches systemic circulation whilst avoiding 1st pass metabolism
- Patches can be easily and quickly removed
- High potent compliance
What are the advantages of transdermal patches?
- Avoids the harsh environment of the GI tract
- Drug reaches systemic circulation whilst avoiding 1st pass metabolism
- Patches can be easily and quickly removed
- High potent compliance
What are the limitations of transdermal patches?
- Low dose of drug
- Drug needs to meet specific physiochemical criteria for delivery
Name the approved transdermal patches? (9)
- Scopolamine
- Nicotine
- Estradiol
- Fentanyl
- Buprenorphine
- Testosterone
- Glyceryl nitrate
- Methylphenidate
- Selegiline MOI
What is scopolamine for?
Motion sickness
What is nicotine for?
Smoking cessation
What is estradiol used for?
HRT
What is fentanyl used for?
Chronic pain
What is buprenorphine used for?
Chronic pain
What is glyceryl nitrate used for?
Angina
What is methylphenidate used for?
ADHD
What is selegiline MOI used for?
Parkinsons disease
What are the three different types of patches?
- Simple drug in adhesive patch
- Drug in matrix patch
- Rate limiting membrane type patch
