Percutaneous Absorption

Question 1

Percutaneous Absorption

Answer 1

Is the passage of drugs from the outside through the cutaneous structures and the extracellular fluid to the blood stream.

Question 2

PA process consists of two steps:

Answer 2

Penetration phase: the passage of molecules through the superficial skin structures (stratum corneum and epidermis) to the extracellular fluid.

Resorption phase during which a relatively rapid diffusion occurs from the extracellular fluid to the blood via cutaneous microcirculation

Question 3

Rate-limiting Barrier

Answer 3

The principal barrier function of the skin is almost entirely provided by the stratum corneum that prevents the penetration of chemical substances.

A thin coherent membrane of flattened keratinized dead cells.

It consists of 10-20 layers formed and continuously replaced from the underlying living epidermis.

Question 4

Rate Limiting Barrier*

Answer 4

Adhesion between cells occurs at the altered desmosomes (tight junctional zones between living cells of epidermis)

50% of the cellular content is made up of semicrystalline alpha keratin filaments 6-8nm in diameter. The alpha keratin is embedded in an amorphous Beta keratin matrix rich in disulfide bonds.

Question 5

Insensible Perspiration

Answer 5

Diffusion (down the activity gradient) of water from the living epidermal mass into the environment.

Question 6

Skin deprived of stratum corneum is..

Answer 6

very permeable to chemical substances

Isolated stratum corneum is as impermeable as the entire skin

Dead skin has the same permeability as living skin