EXAM #5: TOPICAL AGENTS Flashcards
What are the layers of the epidermis?
1) Stratum corneum
2) Stratum granulosum
3) Stratum spinosum
4) Stratum basale
*All of which rest on a basal lamina
What is the stratum corneum?
Layer of dead keratinocytes
What are the living layers of the epidermis?
1) Stratum granulosum
2) Stratum spinosum (synthesis of epidermal proteins)
3) Stratum basale (cell division)
What is the major barrier to percutaneous absorption of drugs?
Stratum corneum i.e. the layer of dead keratinocytes
Why is the stratum corneum the major barrier to percutaneous absorption of drugs?
Contains corneyocytes that are:
- Flattened and lipid depleted keratinocytes
- Plasma membrane has been replaced with protein
- Secrete lipids that are hydrophobic
What is the rule of thumb for choosing a vehicle for delivering drugs via the skin?
If it is wet, dry it; if it is dry, wet it.
What types of vehicles should be used in the scalp and hairy areas?
Lotion Gels Solution Foams Aerosols
What types of vehicles are good for intertriginious areas (two skin areas rubbing together)?
Creams
Lotion
Solutions
What vehicles are best for wetting?
Ointment
Creams
Gels
Lotions/solutions
What vehicles are good for drying?
Aerosols
Pastes
Powders
Tinctures
What is PCA?
Percutaneous Absorption
What factors affect PCA?
1) Concentration of drug in the vehicle
2) Drug diffusion coefficient/ molecular size (less MW gets absorbed faster)
3) Lipophilicity
4) Thickness of the stratum corneum
5) Cutaneous vasculature
6) SA of absorptive surface
7) Mucosal surface
How will skin inflammation affect PCA?
Inflammation will increase systemic absorption
How does skin hydration alter PCA?
Increased hydration increases PCA
How will occlusion of a topical medication i.e. in plastic wrap alter PCA?
Increase PCA
Explain the basic pathophysiology of acne.
1) Follicular epidermal hyperproliferation causes the formation of a “plug” limits the exit of sebum from the follicle
- Plus = “comedome”
2) Keratin, sebum, and bacteria* accumulate and cause inflammation
*Propionibacterium acnes
What topical antibiotics are used to treat acne?
1) Erythromycin
2) Clindamycin
3) Metronidazole
4) Sodium sulfacetamide
5) Azelaic acid
6) Benzoyl Peroxide
What is the MOA of Erythromycin and Clindamycin to treat acne?
- Inhibit protein synthesis
- Directed against P. acnes bacteria
What is the MOA of Metronidazole to treat acne?
Kills bacteria by disrupting DNA
What is the MOA of Sodium Sulfacetamide?
Kills P. acnes by inhibiting dihydropteroate synthetase activity i.e. folic acid
What bacteria are treated with Azelaic acid?
P. acnes and S. epidermidis
What is the MOA of Azelaic acid?
1) Reduces inflammation (free radical scavenging)
2) Reduces keratinization
3) Keratolytic effects cause desquamation