Lecture 26 Flashcards
(35 cards)
What are the conventional dosage forms for drug delivery?
Oral: Tablets, capsules
Transdermal: Creams, ointments, patches
What are the key objectives of the lecture on transdermal delivery?
Opportunities & barriers for skin delivery
Factors affecting skin absorption
In vitro testing of skin absorption
Formulation strategies for herbal product delivery
What functions does the skin serve as a drug delivery site?
Protection, sensation, thermoregulation
What is the main barrier in the epidermis?
Stratum corneum (SC)
What is the structure of the stratum corneum described as?
Brick and mortar model (keratinised cells in lipid matrix)
What components make up the lipid matrix of the stratum corneum?
- Ceramides
- Fatty acids
- Cholesterol
What are the routes of penetration through the skin?
- Transcellular
- Intercellular
- Via appendages (e.g., hair follicles)
Which physicochemical factor affects drug absorption through the skin?
Partition coefficient (K)
How does molecular size affect skin absorption?
Smaller molecules penetrate better
What role does skin hydration play in absorption?
Increases permeability
What pH condition enhances drug absorption through the skin?
Unionised forms absorb better
What drives diffusion in skin absorption?
Concentration gradient
How does age affect skin absorption?
Elderly = less hydrated; infants = thinner SC
Which body site has the highest permeability?
Genitals
What methods can increase skin permeability?
- Hydration
- Soaking
- Occlusion
- Humidity
What is the purpose of the Franz Diffusion Cell?
Measures permeation through membranes
What type of products is the Franz Diffusion Cell used for?
Herbal products like Cordia verbenacea (Acheflan®)
What animal models are commonly used for in vivo skin testing?
- Pigs
- Rats
- Mice
- Guinea pigs
- Snakes
What does IVIVC stand for?
In Vitro–In Vivo Correlation
What is a key advantage of transdermal delivery?
Avoids first-pass metabolism
What are the types of transdermal delivery systems?
- Patches
- Creams
- Ointments
What are the characteristics of patches in transdermal delivery systems?
Occlusive systems increase hydration
What types of patches exist?
- Drug-in-adhesive
- Matrix system (solid drug)
- Reservoir system (liquid drug)
What distinguishes creams from ointments?
Creams: O/W or W/O emulsions in hydrophilic base, short shelf life; Ointments: Greasy, oil-based, longer shelf life, high viscosity
