2. CONTENTS
1. INTRODUCTION
2. ADVANTAGES
3. DISADVANTAGES
4. DRUGS PRESENT IN THE MARKET AS TDDS ?
5. PHYSIOLOGYAND ANATOMY OF SKIN
6. EPIDERMIS
7. DERMIS
8. HYPODERMIS
9. SKIN BARRIER
10. FUNCTION OF SKIN BARRIER
11. REFERENCE 2
3. INTRODUCTION
DEFINATION :
Transdermal drug delivery systems (patches) are dosage forms
designed to deliver a therapeutically effective amount of drug
across a patient’s skin also defined as Medicated adhesive patch
that is placed on the skin to deliver a specific dose of Medication
through the skin and into the blood stream.
Transdermal patch has a coating of medicine (drug), that is placed
on the skin to deliver specific dose of the medicine, into the blood
over a period of time.
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4. ADVANTAGES OF TDDS
Easy to use.
Avoid GIT absorption problems for drugs.
Avoids FP hepatic metabolism of drugs.
More improved and convenient patient compliance.
Rapid termination in case of toxicity is possible.
Self medication is possible.
Reduces frequency of dosing
Maintains therapeutic level for 1 to 7 days.
Controlled delivery resulting in more reliable and predictable blood
levels.
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5. DISADVANTAGES OF TDDS
Daily dose of more than 10mg is not possible.
Local irritation is a major problem.
Drug requiring high blood levels are unsuitable.
Drug with long half life can not be formulated in TDDS.
Uncomfortable to wear.
May not be economical.
Barrier function changes from person to person and within the
same person.
Heat, cold, sweating (perspiring) and showering prevent the
patch from sticking to the surface of the skin for more than one
day. A new patch has to be applied daily.
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7. Physiology and anatomy of skin
o Skin is the part of Integrated system i.e. it helps to maintain body temp and
protect It from surrounding environment.
o It covers an area of about 2m2 and 4.5-5 kg i.e. about 16% of total body weight
in adults.
o Thickness is in range of 0.5mm (on eyelids ) to 1.5mm ( on heels )
o Skin has mainly 3 layers…
Epidermis
1. Stratum Cornium
2. Stratum lucidum
3. Stratum Granulosm
4. Stratum Spinosum
5. Stratum Basale
Dermis
Subcutaneous layer
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9. EPIDERMIS
Epidermis, "epi" coming from the Greek meaning "over" or
"upon", is the outermost layer of the skin.
The epidermis has five regions and can range in total thickness from
0.5mm (eyelid) to 1.5mm on the palms and soles
It forms the waterproof, protective wrap over the body's surface
which also serves as a barrier to infection and is made up of stratified
squamous epithelium with an underlying basal lamina.
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11. DERMIS
o The dermis is the layer of skin beneath the epidermis that consists
of epithelial tissue and cushions the body from stress and strain.
The dermis is tightly connected to the epidermis by a basement
membrane.
o It also harbors many nerve endings that provide the sense of touch
and heat. 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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13. HYPODERMIS / Subcutaneous
o The subcutaneous tissue (also hypodermis and subcutis) is not part
of the skin, and lies below the dermis of the cutis.
o Its purpose is to attach the skin to underlying bone and muscle as
well as supplying it with blood vessels and nerves.
o It consists of loose connective tissue, adipose tissue and elastin.
o The main cell types are fibroblasts, macrophages and adipocytes
(subcutaneous tissue contains 50% of body fat) fats serves as
padding and insulation to the body.
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14. SKIN BARRIER
First time, in the 20th century, Marchionini and Schade applied scientific
evidence for the protective function of the water-lipid mantle of the skin
and introduced the concept of the skin barrier.
According to the definition, barrier refers to an object that separates two
distinct spaces and/or prevents the free passage between two environments.
In this sense, the skin barrier ensures the integrity of the body and
controls the exchange of substances with the environment.
The concept of skin barrier has been constantly evolving in parallel with
the advance of the research methods.
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15. COMPOSITION OF SKIN
Skin is made up of three layers. The outermost is the epidermis. This
consists mainly of cells called keratinocytes, made from the tough
protein keratin (also the material in hair and nails). Keratinocytes form
several layers that constantly grow outwards as the exterior cells die.
The epidermis also contains melanocytes, Langerhans cells, Merkel
cells, and inflammatory cells. The stratum basale is primarily made up
of basal keratinocyte cells, which can be considered the stem cells of
the epidermis.
Chemical composition of skin are: Mainly Carbon, Nitrogen,
Hydrogen and Oxygen with small amounts of Phosphorous Iron,
Sodium, Magnesium, Sulphur, Calcium and Chlorine and traces of
many others. The composition of skin is virtually the same as the
average for the body.
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16. STRATUM CORNEUM
o Currently, it is considered that over 90% of the skin barrier function
resides in the epidermis and particularly in its outermost layer that is
Stratum Corneum.
o Stratum Corneum was considered an inert layer of dead cells formed in
the keratopoesis, interconnected through intercellular lipid layer.
o The Stratum Corneum is a multilayered tissue composed of flattened,
anucleate corneocytes, surrounded by multiple planar lamellae sheets,
enriched in ceramides, cholesterol, and free fatty acids (FFA). The
localization of these highly hydrophobic lipids within the extracellular
domains of the Stratum Corneum inhibits the outward movement of water.
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17. FUNCTION OF SKIN BARRIER
This barrier accomplishes a whole set of critical defensive
functions those are:-
Keep the body water inside.
Keeping microbes and foreign molecules out.
Example:- The Stratum Corneum also blocks the penetration of
ultraviolet light, filtering much of it out before it even reaches deeper
into the skin, where most of the pigment or ‘melanin granules’ reside.
Melanin is in fact only the second line of defence against the
penetration of ultraviolet rays. 17
21. Questions…..????
1. Why drugs with long half life cannot be
permeated in tdds?
2. What are the composition of skin?
3. Physiology of skin?
4. Advantages and disadvantages of skin?
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Editor's Notes
(fp )Floating point hepatic metabolism
Drug with no long half life: means rate of time taken by drug to no longer be in the blood stream.
Pd = when substance moves from higher concentration to lower concentration
Sonophoresis: is a process were exponentially increases the absorption of topical compounds (td) into the epidermis and dermis of the skin.
Iontophoresis : is a process of tdd by use of voltage gradient on the skin.
KERATINISED CELL ; are present in stratified squamous keratinized epithelium which is flat but no longer aive ,basically filled with protein called keratin which makes our skin waterproof.
Startum basale ;made up of keratinocyte stem cell, which is considered as stem cell of epidermis
Arrector pili muscle =small muscle attached to the hair follicle ,while contraction of these muscle causes hairs to stand or end .
Fibroblast : a cell in connective tissue which produces collagen and other fibers
Macrophage : engulfing and destroying pathogens
Adipocytes : calld as lipocytes specialized in storing energy as fat