Week 7 Pharmacokinetics and Biopharmaceutics 2 Flashcards
What are the three site of absorption
stomach
small intestine
large intestine
Why is larger surface area beneficial
if the amount of api absorbed per unit area of GIT is a constant then the more area you have the faster the rate of the absorption
What is gastric residence time
amount of time the drug stays in the stomach
what factors affect the gastric residence time
Type of dosage form
Presence of food
Posture
Disease states
Effect of other drugs upon gastric motility
Half time to empty
What are the 4 absorption mechanisms
passive transport diffusion
facilitated transport
active transport
endocytosis
What is passive transport
API moves from region of high API conc to region of low API Conc
What is the rate of diffusion dependent on
ficks 1st law
which takes
surface area
travel pathway
concentration gradient into account
What is facilitated diffusion
helped across the membrane by carrier molecules
no energy
concentration driven
What is active transport
helped across the membrane by carrier molecules that do require energy input capable of moving APIs against a concentration gradient
what are 3 key physicochemical factors
solubility
pka
log p
what is log p
partition coefficient of the concentration of octanol vs concentration of the api in aqueous
what does a negative log p indicate
preference for aqueous
what does a positive log p indicate
preference for fatty
What is the acid dissociation constant
Ka = to disciated acid conc versus conc of undiscociated
pKA = - log Ka
larger the pka means what
weaker the acid or stronger base
