Lec 2 Part 1 Factors Affecting Absorption Flashcards
..
What are the physicochemical factors that affecting percutaneous absorption?
1_partition coefficient 2_molecular size 3_drug concentration 4_ temperature 5_PH
What is the partition coefficient?
Is the distribution of chemical compound between two phases.
If the drug partitioning coefficient is > 1 it is more hydrophilic (T or F) ?
F more lipophilic
If drug partioning coefficient is <1 then the drug is more hydrophilic (T or F)
T
In which case of partioning coefficient the drug wont be able to penterate the aqueous barrier of the skin?
If the partioning coefficient is very high
In which case of partioning coefficient the druge wont be able to penetrate the lipid barrier?
If the partitioning coefficient is very low.
The amount of drug absorbed will increase as the concentration of drug decrease.(T or F)
F
As the concentration of drug increase
Higher the concentration of drug in vehicle faster the absorption (T or F)
T
The diffusion coefficient decrease as the temperature falls. (T or F)
T
Drugs are preferred to be : 1-strong ionized acid /base 2_strong unionized acid/base 3_weak ionized acid/base 4_weak unionized acid /base
4_weak unionized acid/base
Only ionized molecules pass readily across lipid membrane (T or F)
F unionized
What are the biological factors affecting the absorption?
1_ skin metabolisim 2_skin hydration 3_ skin age 4_skin condition 5_ regional skin site 6_blood flow
As the blood flow increased the amount of time a pentrate remains in the dermis decreased (T or F)
T
The high blood flow raises the concentration gradient across the skin (T or F)
T
How the regional skin sites affecting the absorption ?
Variation in cutaneous permeability around the body depend on the thickness and nature of the stratum corneum and the density of the skin appendages
How we can make the drug effective in the skin only and don’t enter the circulation system ? (Localy drugs)
By using the SOFT DRUGS which are active in the viable epidermis and dermis, skin enzymes bio transform them into inactive metabolites. The active drug therefore dose not enter the circulating system and the pharmacological effect is limitef to the application area.
What is the importance of water in absorption of drugs?
Water is natural plasticizer to the skin making its lipid content less rigid(صلابة) by fluidization its crystalline structure. And also hydrates the skin keratin fibers making them softer and more permeable ..where hydrated skin much more permeable than dry skin.
Give reason Urea is included in some topical preparations for transdermal drug delivery.
Because the urea act as natural moisturizing factor(NMF)and as a keratolytic agent
What is the natural moistureizing factor(NMF)?
It is substance which increase water content of the skin by being able to bind with water to the skin cells.
What is the occlusion?
Forming a layer over the skin to prevent evaporation of sweet which accumulates under such layer causing very efficient skin hydration.
How can we increase the water content of the skin?
1_By using occlusive vehciles
2_ by using natural moisturizing factors
