Percutaneous Absorption
Session 4: Percutaneous Absorption
Total Session Time: 120 minutes
Prerequisites
Learning Tasks
By the end of this session students are expected to be able to:
Explain percutaneous Absorption
Explain factors affecting percutaneous absorption
Resources Needed:
SESSION OVERVIEW
Activity/
Step Time Content
Method
1 05 Minutes Presentation Introduction, Learning Tasks
50 Minutes Presentation
2 Percutaneous Absorption
Brainstorming
55 Minutes Presentation
3 Factors Affecting Percutaneous Absorption
Buzzing
4 05 Minutes Presentation Key Points
5 05 Minutes Presentation Evaluation
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SESSION CONTENTS
STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)
READ or ASK students to read the learning tasks and clarify
ASK students if they have any questions before continuing.
STEP 2: Percutaneous Absorption (50 minutes)
Activity: Buzzing (5 minutes)
ASK students to pair up and buzz on the following question for 2 minutes
ALLOW few pairs to respond and let other pairs to add on points not mentioned
WRITE their response on the flip chart/board
CLARIFY and SUMMARIZE by using the content below
skin and subsequent movement into the systemic circulation.
o The medicament is released from the base
o Adequate amount of drug penetrate the skin
o Sufficient concentration of the drug is maintained at the site of action.
medicament
applied topically purposely for:
o Skin protection (against sunlight or moisture loss
o For emollient effect
o For antimicrobial activities in skin disinfection
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longer as possible in the viable epidermis and dermis with minimal elimination by systemic
circulation.
mechanism by which medicaments penetrates the skin barrier.
o The skin is divided into three layers:
epidermis
dermis
hypodermis (subcutaneous fat layer)
o Is about 110µm thick
o Is pierced by hair follicles & sebaceous gland
o It is non vascular
o The outer layer of the epidermis is called stratum corneum
o The stratum corneum is transparent, tough coherent & viscoelastic properties.
o The stratum corneum is composed of dead cells each packed with keratin.
o Resistance to the diffusion of chemicals is greater in stratum corneum (sc) than in the
underlying living skin tissue.
o SC is the rate-limiting barrier to movement of materials & responsible tissue for
impenetrability of the skin.
o However the is not an absolute barriers and trace amount of penetrants can be detected; eg
nickel, chromium ions, parathion & toxic gases.
o The thickness of sc varies. It is thick on the plantar & palmar areas and thin behind the ear and
on the eyelid.
o Cells are formed through mitosis at the basale layer
o The daughter cells move up the strata changing shape and composition as they die due to
isolation from their blood source
o The cytoplasm is released and the protein keratin is inserted.
o They eventually reach the corneum and slough off (desquamation).
o This process is called keratinization and takes place within about 27 days.
o This keratinized layer of skin is responsible for keeping water in the body and keeping other
harmful chemicals and pathogens out, making skin a natural barrier to infection.
o The dermis is the layer of skin beneath the epidermis that consists of connective tissue and
cushions the body from stress and strain.
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o The dermis is tightly connected to the epidermis by a basement membrane.
o It also harbours many Mechanoreceptor/nerve endings that provide the sense of touch and
heat.
o It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic
vessels and blood vessels.
o The blood vessels in the dermis provide nourishment and waste removal from its own cells as
well as from the Stratum basale of the epidermis.
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o The hypodermis lies below the dermis
o Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with
blood vessels and nerves.
o The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains
50% of body fat). Fat serves as padding and insulation for the body.
Figure: 1.4. Structure of skin
Source: Human Anatomy by Matthew Hoffman, MD (2014)
STEP 3:Factors Affecting Percutaneous Absorption (55 minutes)
Activity: Brainstorming (20 minutes)
Ask students to brainstorm on the following question:
ALLOW few students to respond?
WRITE their responses on the flip chart/ board
CLARIFY and SUMMARISE by using the content below
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o Condition of the skin
o Physicochemical characteristics of the active substance
o Effect due to the vehicle.
o Damage and disease.
Intact skin presents a barrier to absorption that can be reduced considerably when the skin
is damaged or is in a disease state.
Skin can be damaged by:
o Injured skin has increased percutaneous than intact skin.
o Percutaneous absorption of infants is higher than in adult to a given medicament due to
large surface area than that of adult
Partial developed epidermal drug metabolizing enzymes.
o Old age can also affect permeability of the skin through change in the elasticity, ultrastructure,
chemical composition & barrier properties.
o Absorption is influenced by environmental factors such as skin temperature & surface
humidity,
o Diffusion can be accelerated by raising surface temperature e.g. by occlusion
o Fick‟s law of diffusion states that the diffusion of a solute will be inversely proportional to the
thickness of stratum corneum.
o In the plantar & palmar the SC is thick & absorption rate is low than in thin thickness like on
face & behind the ear.
o Absorption of active substance is enhanced as the skin become more hydrated.
o Topical medicament with occlusive effect has high absorption rate than the non-occlusive
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o The application of vasoconstrictor such as steroids on the skins surface may slow penetration
because of the reduced blood supply.
STEP 4: Key Points (5 minutes
skin and subsequent movement into the systemic circulation.
from the base, adequate amount of drug penetrate the skin and sufficient concentration of the drug
is maintained at the site of action.
characteristics of the active substance and effect due to the vehicle.
STEP 5: Evaluation (5 minutes)
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References
through diffusion cell". J. Pharm. Sci. 74: 64–7. doi:10.1002/jps.2600740117.Sudan
Mahato RA. (2006) Pharmaceutical dosage forms & drug delivery‟‟ Published by CRS press, Taylor
& Froncrs Group,6000 Broken Sound Parkway, Sute 300, Boca Raton, 196-197.New York
A. J. Winfield, J. A. R., I. Smith. (2009). Pharmaceutical Practice (4th ed.) British
Britain, R. P. S. o. G. (1994). The Pharmaceutical Codex (12 ed.). London: London
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