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Percutaneous absorption Ms.Wajiha Iffat

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					      Percutaneous absorption
           Ms.Wajiha Iffat
                    Objective:
After the end of this lecture, student will be able
                        to :
•Describe Structure of skin
•define the percutanous absorption
•Its importance
•Factor affecting percutaneous absorption
•Ways to maximize drug bioavailibility
       Percutaneous Absorption
• Skin also known as cuteneous membrane or
  integument .
• It means any external membranous covering
  or integument of an animal body.
• Skin is the largest organ of the body ,it is thin
  at some places (eye lids thickness =0.5mm)
  where as thick at other places (sole of foot,
  palm of hand thickness=5mm).
• Average thickness of skin is 1-2mm.(0.04-
  0.08in).
      Percutaneous Absorption
• In adults, the skin covers an area of about 2
  square meter and weight 4.5-5kg, about 16%
  of total body weight.
        Percutaneous Absorption
• Skin is made up of two layers,
1.Outer epidermis,
2.Inner dermis.
• 1:-Epidermis
 epi =above , dermis=skin
• It is the superficial , thinner portion
composed of keratinized stratified squamous
epithelial tissue.
       Percutaneous Absorption
• Epidermis replaces itself . about every two and
  half months.
• It has no blood vessel but it is nourished by
  diffusion of nutrients from a vascular network of
  dermis.
• It is composed of 4 type of cells
1-keratinocytes
2-melanocyets
3-langerhans cell
4-merkel cell.
         Percutaneous Absorption
keratinocytes
keratino=horn like, cytes=cell
• 90% of epidermal cells are keratinocytes.
• These are arrange in 4 to 5 layers and are responsible for
   production of protien keratin,which is a tough fibrous protein
   responsible to protect the skin and underlying tissues from heat,
   microbes and chemical.
Melanocytes
Melano=black, cytes=cell
• 8%of epidermal cells are melanocytes.
• They produces a pigment melanin (a yellow red or black brown
   pigment) contribute in skin colour and also absoorbs damaging u-v
   light
      Percutaneous Absorption
Langerhans cells
• They participate in immune responses against
  microbes that invade the skin and they are
  easily damaged by u-v light.
• Helps other cells of immune system to
  recognize an invading microbe and destroy it.
Merkel cell
• Participate in detection of touch sensation.
        Percutaneous Absorption
DERMIS :
 The sensitive connective tissue layer of the skin located
  below the epidermis, containing nerve endings, sweat
  and sebaceous glands, and blood, hair follicles,
  fibroblast , histocytes and lymph vessels. Also called
  corium, cutis, Also called derma.
• Composed of strong connective tissue containing
  collagen ( for strength ) and elastin ( for stretch )
• Derma blood vessels not only supply blood to the
  dermis and epidermis but also play major role in
  temperature regulation.
       Percutaneous Absorption
Hypodermis :
• Below the dermis is hypodermis also k/as
  subcutaneous layer
• Sub mean under and cutaneous mean skin.
• It is a loose layer of connective tissue which is
  anchored to the underlined tissue ( muscle and
  bones).
• Most fats cells are present in hypodermis
  collectively known as adipose tissues act as
  insulator to protect the body from excessive heat
  and cold environment
        Percutaneous Absorption
Appendages of the skin:
• Hair follicles with hair
• Nails
Glands of skin:
• There are two types of glands
• Sweat glands
• Sebaceous glands
Sebaceous glands :
• They are simple or branched alveolar glands situated in the
  dermis of skin
• They secrete an oily secretion c/as sebum active at the time
  of adolescense.
      Percutaneous Absorption
Percutaneous Absorption:
  Percutaneous absorption involves the transfer
  of drug from skin surface in to stratum
  corneum, under the aegis of a concentration
  gradient and its subsequent diffusion through
  the dermis and in to microcirculation the skin
  behaves as a passive barrier to diffusing
  molecules
       Percutaneous Absorption
• Percutaneous absorption of a drug generally
  results from the direct penetration of the drug
  through stratum corneum,10-15µm thick layer
  of flat partially desiccated non living tissues.
• SC is composed of 40%protein & 40%water
  with a balance being lipid.
• SC acts as a semi permeable membrane &
  drug molecules penetrates by passive
  diffusion. it is the most rate limiting barrier to
  TDDS TRANSPORT.
     Percutaneous Absorption
RATIONAL APPROACH TO DRUG DELIVERY TO &
  VIA THE SKIN:
• Surface treatment
• Strarum corneum treatment
• Skin appendage treatment
• Viable epidermis & dermis treatment
• Systemic treatment via transdermal
  absorption
     Percutaneous Absorption
FACTOR AFFECTING PERCUTANOUS
  ABSORPTION:
BIOLOGICAL PARAMETERS:
• Skin condition
• Skin age
• Blood flow
• Regional skin sites
• Skin metabolism
      Percutaneous Absorption
PHYSICOCHEMICAL PARAMETERS:
• Physicochemical Attraction Of Drug
• Mol Wt Of Drug
• Hydration Of Skin
• Temperature & pH
• Drug Concentrations
• Diffusion coefficient
• Partition coefficient
• Area Of Applications
• Contact Time
      Percutaneous Absorption
MAXIMIZING THE BIOAVAILIBILITY OF DRUG TO
  SKIN:
• Drug or pro drug selection
• Hydration
• Ultrasounds(phonophoresis)
• Ionophoresis
• elctroporation
• Stratum corneum removal
• Microneedle array
• Chemical penetration enhancers

				
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posted:7/30/2011
language:English
pages:18