Topical

Question 1

Describe the Stratum Corneum

Answer 1

• Rate limiting step for Percutaneous absorption
• Made up of a Corneocytes
  
  • flattened and lipid-depleted keratinocytes that contain filaments composed of keratin granules
  • plama membrae is replaced by an envelop of insoluble protein (cornifed envelop)
  • lipids are extruded into the extracellular spaces

Question 2

What are teh various routes of absorption pathways of intact skin

Answer 2

• Through appendages (shunt route)
• Transcellular route (trhough corenocytes of stratum corneum)
  
  • corneocytes contain highly hydrated keratin which allows hydrophilic drugs to pass through
• Through intercellular lipid domains
  
  • Most common route of absorption for SMALL UNCHARGED molecules

Question 3

describe vehicles selection based on area of body

Answer 3

• Lotions, gels, solution, foams, and aerosols are convenient for SCALP AND HAIRY AREAS
• Creams, lotions and solutions may be used in INTERTRIGINOUS AREAS (two skin areas may rub together) without causing maceration

Question 4

Describe vehicle selection based on condition of the skin

Answer 4

• DRY and SCALY SKIN
  
  • Wetting agent
    
    • Ointments –> creams –> gels –> lotions.solutions
• WET and OOZING SKIN
  
  • Drying agents
    
    • Tinctures –> powders –> pastes –> aerosols

Question 5

What are the DRUG factors affecting PERCUTANEOUS ABSORPTION (PCA)

Answer 5

• Conc of drug in vehicle
  
  • PCA is direclty related to conc
• lipophilicity of drug
  
  • More lipophilic… increase in PCA
• molecular size
  
  • smaller the molecule… Increase in PCA

Question 6

Factors of the innate skin that affect Percutaneous absorption

Answer 6

• Stratum corneum thickeness
  
  • INVERSELY related to PCA
• Cutaneous vasculature
  
  • increase in vasculature… Increase in both local and system drug effects
• Absorptive surface
  
  • increased Surface area… Increase PCA total overall
• Mucosal surface
  
  • far less innate barrier function, so better absorption and risk of systemic effects

Question 7

Other variables affected percutaneous absorption

Answer 7

• Inflammed/ulcerated Skin = overall Increase PCA
• Skin hydration
  
  • hydrating skin prior to application of topical medication will INCREASE PCA
• Occlusion of medicaiton (wrapped in food wrap)
  
  • topical occlusio locally = marked increase PCA
• Age of patient
  
  • infants and young childrean have INCREASE RISK OF SYSTEM EFFECTS from TOPICAL THERAPY due to icnreased total body surface area to body volume ratio

Question 8

What areas have the most penetration

Answer 8

mucous membrane

scrotum

eyelids

face

chest and back

arms and legs

dorsa of hands and feet

palmar and plantar skin

nails

Question 9

Describe the prinicples when initiating topical corticosteroid therapy

Answer 9

• Initiate LWOEST POTENCY to sufficiently control disease
• when LARGE surface areas are involved, tx with low to medium potency
• Low-potency used on face and intertriginous areas and very potent required for palms and soles
• avoid high potency preparations in infants and young children
• Tachyphylaxis (diminished therapeutic benefit) can occur when High potency class corticosteroids are applied daily for 2 weeks
  
  • can prevent by alternate day applications

Question 10

Atopic dermatitis (eczema)

Answer 10

• chronic inflammatory skin disorder associated with INTENSE PRURITUS and DRIED FLAKING SKIN
• predisposing factors that inhibit epidermal barrier dysfunction significantly elevate risk
• TX WITH CORTICOSTEROIDS
• often need antibiotics for secondary bacterial infections