Topical terminology Flashcards
Topical drug delivery
The application of a formulation to the skin to treat a local disorder where the API acts within the skin or in the underlying tissue
Transdermal drug delivery
The application of a formulation to the skin to deliver a drug to the systemic circulation (e.g. fentanyl patches).
Locally acting
Active pharmaceutical ingredient acts directly on the skin
Regionally acting
API acts in the area close to where the formulation is applied. Often described as locally acting but drug does not act directly on the skin
Permeant
chemical species that is moving into or through the tissue this is the API and other ingredients of the formulation
Permeation
movement of permeant through the skin
Penetration
entry into the tissue does not require the molecules to pass out the tissue
Diffusion
movement of molecules through a domain from an area of high concentration to one of low concentration by random molecular movement
diffusivity
property of the permeant in the membrane to see how easily it traverses the tissue
diffusion coefficient (D)
area per unit time often related to diffusivity
permeability coefficient KP
describes the speed of permeant transport given as distance per unit time
partition coefficient (P/kp/logp)
measure of the distribution of molecules between two phases octanol and water
often being used as a guide to see how well a molecule will distributre between the stratum corneum lipids and water.
partitioning
process of molecules distributing themselves between two domains in transdermal drug delivery and used to describe molecular redistribution from one domain to another
flux (J)
rate of a permeant crossing the skin it is given in units of mass per area per time
lag time (L)
this is obtained from a permeation profile by extrapolating the steady state flux line to the time axis
