Pharmokinetics 2 Flashcards
Describe what metabolism is refering to:
(3rd step of pharmocokinetics)
-making drugs more water soluable, so kidneys can excrete them into urine
Where does metabolism of a drug mostly occur?
In the LIVER!!!
What is the goal of metabolism?
to make sure drugs are hydrophilic, so they can get peed out
What are some factors that effect meatabolism?
-Age
-p450 system
-first pass effect in liver for PO meds
-nutritional status, competion between drugs
what is the p450 system?
a family of enzymes (proteins) in our liver that metabolize drugs for excretion
How many enzyme families/pathways do we have in our liver?
total of 12.
3 of them are responsible for metabolizing drugs for excretion
p450 inhibitior:
decreases metabolic activity of enzyme
p450 substrate
a drug that is metabolized by that p450 enzyme.
the product
p450 inducer:
increases metabolic activity of enyme
Describe the first pass effect
-rapid inactivation of some oral meds
-happens ONLY with PO meds
-when a medicine gets inactivated through first pass of liver
Enterohepatic circulation
(also what does it result in)
when a drug given PO gets hydrolyzed amd gets caught in a cycle between GI tract and liver.
this results in drugs staying in the body longer
Describe excrertion (AKA the last and final step of pharmacokinetics)
removal of drugs from body
where does excretion mainly occur?
mainly occurs in the kidneys
What does peak refer to?
-when the drug is at the highest level in the body
what are some factors that effect excretion?
-PH (ions), age, competion for active tubular transport
What does trough refer to?
-when the drug is at the lowest level in the body
minimum effect concentration (MEC):
minimum amount of drug needed to have any effect
toxic concentration
too much drug. this will lead to toxic effects
therapeutic index
goal area to reach. just the right amount of effect
What is a loading dose given for?
a larger dose given to reach desired level
define “half life” of a drug
length of time it takes for drug to decrease by 50%
what does it mean when a drug reaches its plateau?
plateau is reaches when
drug eliminated=drug administered
how many half lives does it take for a drug to reach a plateau?
4-5 half lives
Drug levels ______ with absorbtion
INCREASE
