Pharmacokinetics Flashcards
what does ADME stand for
absorb
distributes
metabolize
eliminate
what determines the intensity of the drugs effect
the concentration at the site of the receptor
what are the routes of administration
oral IV subcutaneous intramuscular transdermal pathc rectal inhalation sublingual
3 ways drugs cross the cell membrane
pass through channels or pores
through membrane with transport system
penetrate directly if lipophilic (most common)
where are transporters found
liver
kidney
intestine
brain capillaries
how is 2 compartment model different from one compartment
in two drugs are not distributed instantaneously to peripheral, there is a time lag
what kinds of drugs are best described by one compartment model
drugs that dont extensively distribute into extravascular tissues
what is another word for bioavailability
absorption
describe bioavailability
fraction of unchanged drug that reaches the blood
what is drug accumulation
inversly proportional to dose lost
describe volume of distribution
how drug is distributed in body relative to plasma
define clearance
ability of the body to eliminate the drug
what is the drug half life
time required to change the amount of drug in the body by one half
what does AUC stand for
the area under the curve of a graph of plasma concentration against time
what is the % bioavailability in IV admin
100%
what is the first pass effect
drugs metabolized and inactivated in the liver
describe enterophepatic cycling
body recycles the drug from liver to bile duct back into the intestine, hepatic artery, liver again
prolongs half life
8 factors that influence drug absorption
fromulation water solubility lipid solubility pka Gi motility posture others drugs/food gastric ph
is the drug charged or uncharged when passing through a membrane?
uncharged
acidic drugs require what environment to pass through the membrane
acidic environment so they are in the uncharged HA form (dont ionize in acidic)
basic drugs require what environment to pass through the membrane
alkaline environment so it is in the uncharged form B (dont ionize in basic)
how many half lives does it take for a drug to be fully accumulated or eliminated
4
what is steady state
when rate of drug elimination equals rate of administration
what does a high volume of distribution represent
drug is extensively distributed and not in the plasma
what is the loading dose
Vd x desired plasma concentration
how do you calculate volume of distribution
total amount of drug in body/ plasma concentration
what is th epurpose of the loading dose
reach therapeutic range right away
what are the phase 1 reactions
oxidation
reduction
hydrolysis
what are the phase 2 reactions
glucuronidation
sulfation
acetylation
what is the result after phase 1 reactions in metabolism
usually an inactive metabolite by adding or exposing a polar group
what is the result of phase 2 reactions
a conjugated derivative
what is first order metabolism
rate of drug metabolism proportional to dose
what is zero irder metabolism
enzyme is saturated and the rate of drug metabolism remains constant overtime
what are 6 consequences of phase 1 +2 metabolism
accelerated renal excretion drug inactivation activation of prodrugs decreased toxicity increased therapeutic action increased toxicity
define clearance
volume of plasma that must lose all the drug it contains in one minute to account for the observed rate of drug elimination
how many half lives are required to eliminate a single dose of a drug from the body
4-5
what is the importance of clearance
tells efficiency by which a drug is removed from the body
determining maintenance dose and dosing rate
what type of drugs are excreted in urine
non lipid soluble
polar
ionized
low MW
how does aging affect half life (decreased muscle)
decreases half life
how does obesity effect half life
increases
how does pathologic fluid effect half life
increases
how does induction of cyp450 affect half life?
inhibition?
induction decreases
inhibition increases
how does organ failure effect half life
increases
