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33 Cards in this Set
- Front
- Back
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WHAT IS PERCUTANEOUS ABSORPTION
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absorption of drug molecules through the skin namely stratum corneum, viable epidermis, and dermis then reaching the blood vessels
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what does the rate of drug delivery across the SC depend on
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concentration of drug in vehicle
physiochemical properties of the drug (drug aqueous solubility) oil in water partition coefficient between SC and the vehicle properties of the vehicle physical properties of the skin |
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what is the epidermis made of
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stratum croneum (dead cells)
viable epidermis (4 layers) -s. lucidum/mucosum -s. granulosum -s. spinosum (prickle cells) -s. germinativum (basal cells) |
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how are SC cells made
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the cells of the basal cell layer move upwards changing in shape and composition, gradually losing viability until they become horny (dead cells) of the SC layer
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how long does it take the epidermis to renew
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4 weeks
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what are the properties of the Epidermis
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no blood vessels, nerve or lymph channels
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what part of the epidermis has the enzyme capacity
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the viable epidermis where biotransformation can occur via esterase
THIS MEANS DRUGS CAN BE METABOLIZED/DEGRADED HERE |
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what is the stratum corneum made of
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lipid domain
corneocytes |
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what are corneocytes
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cytoplasmic membrane (protein lipid complex) completely filled w/ keratin
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what are corneocytes associated with
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structure water (water crystale)
5-15% normally 50% when highly hydrated |
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what is the lipid domain
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intercellular lamellar lipid sheets
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what are lipids in the SC made of
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40% ceramides
40% cholesterol/cholesteryl esters |
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what are the characteristics of SC
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major barrier of percutaneous absorption
very thin layers 10-15 micro meters, 40 micrometers when fully hydrated lipophillic in nature constantly shedding from the surface b/c scrapping and rubbing **viable epidermis/dermis is 1000x more permeable |
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what is the true skin
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dermis
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what does the dermis have that makes it different from epidermis
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dermis contains blood vessels and nerves
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what are epidermal appendages
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orifice at the surface of the epidermis but reside in dermis
hair follicles subaceous glands sweat glands |
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what are the routes of percutaneous absorption
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TRANCELLULAR DIFFUSION MODE
-intercellular (goes through the lipid domain) -intracellular (goes through the cell, more hydrophillic) TRANSAPPENDAGEAL SHUNTS -hair follicles -sabaceous glands -sweat glands *THIS ROUTE IS FAST BUT LESS SIGNIFICANT |
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why is absorption through appendegeal shunts insignificant
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palms/soles of skin have 3x as many sweat glands than other sites but are less permeable
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what is the fate of drug ,olecules during percutaneous absorption
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drug dissolves
drug diffuses PARTITION INTO SC drug can bind in depot as drug reservoir or contnue to diffuse DIFFUSE IN SC partition into viable epidermis drug can be metabolized bind to receptors or continue to diffuse through viable epidermis partition into dermis drug can be metabolized bind to a receptor or bind to a depot as a drug reservoir IMMUNOLOGICAL REACTIONS OCCURS BECAUSE FORMING DEPOT AND CONTINUE TO METABOLIZE DRUG diffusion in dermis drug reaches blood vessel |
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what is the only drug in internal phase
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emulsion
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what dosage form does only the dissolved fraction act as a penetrant
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suspension
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what mode is dominant in percutaneous absorption
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transcellular diffusion
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what are the physiological factors effecting permeation
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age
skin hydration skin pathophysiological conditions |
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how does age affect permeation
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elderly have thin/dry skin
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how does skin hydration affect permeation
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increase hydration - compactness of keratin decreases
this occurs b/c transportation of water from deeper layer of skin occlusion to prevent water evaporation (accumulation of sweat from perspiration) vehicle capable of absorbing water from atmosphere |
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how does skin pathophysiological conditions affect permeation
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eczema
dermatitis psoriasis ichthyosis |
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what promotes skin hydration the most
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PEG
ANHYDROUS LANOLIN CREAM OIL IN WATER CREAM WATER IN OIL OLEAGINOUS BASE (PETROLATUM) |
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how do you evaluate permeation in vitro
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w/ Franz diffusion cells and test on EXCISED SKIN
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how do you evaluate permeation in vivo
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animal models
human subject |
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how can you chemically inhance permeation
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penmetration enhancers (ethers/sulfoxides/dimethyls)
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how can you physically inhance permeation
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iontophoresis
ultrasound |
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what are concerns of using enhancers
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enhancer permeation and deposition
reversibility toxicity compatibility with excipients FDA regulatory approval |
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what are the chemical enhancers for patches
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Km modification
D enhancement DMSO Propylene glycol Azone |
