MNSR 26 _TDD

• what are examples of penetration enhancers

  chemical additives and physical approaches
• what are surfacants

  they are surface active agents combined with the drug in the transdermal patch , enhance efficacy
• what are examples of surfacants

  they are organic compounds that contain hydrophobic and hydrophilic groups
• what are examples of physical approaches used in penetration enhancement

  iontophoresis, electroporation and microneedling
• what is iontophoresis

  it involves the use of a low electric current applied for several minutes
• what drives iontophoresis

  electrophoretic force which causes electrons to move from the cathode of like charge
• what is electroporation

  creation of pores in the skin using a high voltage current applied for a short time typically milliseconds
• what is microneedling

  it involves the creation of holes in the skin using needles of micron dimensions which are coated in the drug
• when does microneedling take place

  it is a pretreatment before patch is applied
• what do penetration enhancements ultimately do?

  they increase the skin permeability, they allow large molecules such as proteins to pass through the skin
• what are the limitations of transdermal drug patches

  low molecular weight (<500), good water and lipid solubility (balance is key) and only allow small molecules to pass through the skin, neutral rather than ionic drugs, small required dose (<50 mg but ideally <10 mg) and melting point must be lower than 100 degrees celsius.
• what are the disadvantages of transdermal drug delivery 


  possible skin irritation , variation in dosage due to different levels of skin hydration, different thickness of stratum corneum, variation in patients temperatures, skin type, skin of different ages and diseased skin, poor diffusion of large molecules such as proteins and nucleic acids
• what are the advantages of TDD

  reduces the first pass effect in drug delivery, reduces side effects (estradiol patches doesn't cause liver damage in contrast to oral administration) sustained delivery of drug, removal of source at any time
• where is the drug metabolised

  liver
• how much of the drug administered enters the bloodstream after metabolism within the liver

  roughly 1%
• how does the drug reach the liver

  hepatic portal vein
• what is the thickness of the stratum corneum

  10-20 micrometers in thickness