Pharmacokinetics Flashcards
Enteric drugs
administered through the GI tract
4 types of enteric drugs
oral, sublingual, buccal and rectal
What is an advantage of IV meds?
they circulate fast
100% bioavailability
What is an advantage of oral meds?
very safe
cheap
Bioavailability
the amount of drug that reaches systemic circulation
First pass metabolism
lowers bioavailability of drug
4 ways a drug can cross membranes and get into blood
1) Endocytosis
2) Passive diffusion
3) Active transport
4) Pore transport
Indirect active transport
antiport and synport
*still requires ATP to move against gradient, just going with or against another molecule
main pathway for drug transport
passive diffusion
facilitated diffusion
use ATP to directly move substance across membrane
What form must drugs be in to work?
non-ionized
What happens when pH = pKa
~50% of drugs are in non-ionized form
How can you get drugs to be closer to non-ionized form?
put in pH that is similar to their pKa or more extreme
ex: acids will be less ionized in an acidic environment
When will bases be less ionized?
in a basic environment
What is the pH of the stomach?
3.4
When would you want low bioavailability?
if you want an oral drug to target the gut
drug doesn’t need to go to bloodstream
Distribution of drugs
determines where they act, where they are eliminated and how long they last in the body
What does small Vd mean?
drug stays in plasma
Vd < 14 L
you are in plasma
Vd 14-49 L
you are in extracellular tissue
Vd > 50 L
you are in fat
ion trapping
if you place a drug with a certain pKa in an environment where the pH is very different, the drug will become ionized
this can trap the ionized drug in certain environments
What happens is all albumin sites are saturated in blood?
the drug will leave the blood and enter the plasma
serum level of drug drops and tissue level rises
