Delivery of Drugs through the Skin

• What is the role of the skin as a barrier?

  • Prevents loss of physiological fluids
  • Blocks diffusion of materials and microorganisms
  • Allows small, lipophilic molecules to pass
• What is the role of the stratum corneum in drug delivery?

  It acts as a semi-permeable membrane allowing passive diffusion
• What factors affect the diffusion rate of drugs through the skin?

  Drug concentration, aqueous solubility, and oil-water partition coefficient
• How can skin permeability be altered?

  By compromising the integrity of the skin or using permeation enhancement techniques
• What are the types of drug delivery vehicles for topical applications?

  • Solutions
  • Suspensions (lotions)
  • Semisolids (creams, ointments, gels)
  • Solids (patches)
• What are ointments and how do they differ from creams?

  Ointments are viscous formulations with little or no water, while creams contain significant water
• What are gels composed of?

  High molecular weight hydrophilic polymer dispersed in water