pr5216 tutorial lifeng

7/30/2019 PR5216 tutorial Lifeng

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CA test1. Time 1800-1850 on January 28, 2013.

2. Close-book assessment.

3. Format: short questions.

Youtube video showed for lecture

Skin anatomy and biology:http://www.youtube.com/watch?v=yKAzVC0WcmI

Transdermal electroporation

http://www.youtube.com/watch?v=SElfH3e0fQ0

Transdermal laserhttp://www.youtube.com/watch?v=YInx_7w8Oqg

Transderal ultrasonic

http://www.youtube.com/watch?v=E-34gU_7jDY&feature=related

Microneedle, drug coated;http://www.youtube.com/watch?v=2Pp4CE4F3jI

Microneedle pretreatment; Then normal patches.

http://www.youtube.com/watch?v=RVbY5nHPpnw&feature=related

Microneedle hollow, for injectionhttp://www.youtube.com/watch?v=6noG3gQBOyg

Microneedle roller

http://www.youtube.com/watch?v=Asj9q6jTBpo&feature=related


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Short Questions

1. Describe the structure of epidermis and its relevance to the

selection of drug candidates for transdermal and topical drug

delivery.

Epidermis consists of stratum corneum and the rest viable

layers. The stratum corneum intercellular lipids are the major

penetration pathway. Drugs need to partition from carrier to

stratum corneum. Then drugs need to partition from stratum

corneum to the hydrophilic regions of the viable epidermis.

Drugs with high partition coefficients can easily partition into

stratum corneum (lipid in nature) but have difficult partition

into the hydrophilic regions of the viable epidermis. Therefore,

a medium polarity (log P 1-3) is preferred for transdermal

drug delivery. On the other hand, drugs of high lipophilicity

can be good candidates for topical dosage forms as their

targeting sites are skin.

2. Describe the sandwich model for transdermal drug delivery.

The skin barrier is located in the outermost layer of the skin,

the stratum corneum. This layer consists of keratin enriched

cells embedded in lipid lamellae. These lamellae form the

main passages for diffusion of substances through the skin.

Drug can diffuse through the tortuous lipid regions where

lipids are more loosely packed (liquid crystalline phase) than

the densely packed (crystalline phase).The liquid crystalline

phase consists of cholesterol and free fatty acids while the

crystalline phase consists mainly of ceramides.


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3. To deliver a hydrophilic drug through skin to treat bone

cancer, what are potential semisolid dosage forms?

To treat bone cancer, drug needs to be delivered into the

blood circulation. So a transdermal dosage form is needed todeliver drug through skin into blood circulation. For a

hydrophilic drug, hydrogel, emulsion and liposome can be

potential dosage forms.

4. What are the functions of each ingredient in the following

transdermal gel?Methyl Salicylate 5 g (drug)

Carbomer 0.1g (polymeric thickener)

Farnesol 1g (enhancer)

Methyl paraben 0.2g (preservative)

Ethanol water to 100ml (solvents)

5. The oral dose of a drug is 10 mg per day. Its flux in atransdermal patch was determined to be 100 g/(hcm

2).

What should be the patch size?

Assume the bioavailability of this drug is 100% for both oral

and transdermal drug delivery. So 10 mg need to be

delivered in 24 hours. In 24 hours, 2400 g of drug can be

delivered per cm2. To deliver 10 mg, or 10000 g, the patch

size needs to be 10000/2400 = 4.17 cm2

. (You can alsoassume the bioavailability to be 40%, 70%...and calculate

accordingly)


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Long Question

6. A protein molecule (5k Dalton) shows therapeutic effect

when its plasma concentration reaches 1 ng / ml. An in vitro

skin permeation study needs to be carried out to test the

drug permeation rate through skin.

1) Hand-draw a schematic diagram of a flow-through cell forinvitro skin permeation study.

2) Describe a method to prepare the epidermal membranefrom a piece of human skin sample.

Dermatome; hot water at 60 C for 2 minutes; or extract

skin cells to engineer skin if the skin is still viable.

3) If the size of a transdermal patch is 10 cm2

and the plasmaclearance of the drug is 1 litre/hour, calculate thepermeation rate needed for the drug to reach its effectiveplasma concentration.J = Clp*Css/A = (1000 ml/hour) * (10

-3g/ml) / 10 cm

2

= 0.1 g/hour/cm2

pr5216 tutorial lifeng

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