general principles Flashcards
def of distribution
go to highly perfused areas, then drops in plasma conc gets med to leave areas and go out of the body…. goes from highly vasc to less (fat).
first pass effect
drugs from GI pass to liver before circa system= metabolism of drug—> some part of the drug doesn’t make it to target area
absorption depends on
solubility
what not obvious routes of administration avoid first pass effect
sublingual and transmucosa
hepatic clearance
hepatic blood flow and hepatic extraction ratio….
>0.7= dpendent on bf….* perfusion-dependent elimation
<0.3= capacity dependent elimination….
1/2LIFE
body conc to decrease by 1/2
1/2 TIME
time it takes to decrease conc in PLASMA by 1/2.
relationships of e1/2t
directly to Vd, inversely to clearance and protein binding
volume of distribution
dose of iv drug/ [p] before elimination
the sum of all the volumes of the components
clearance
volume of plasma cleared of drug by metabolism excretion
zero-order
exceed metabolism and/or excretion to clear
ex. etoh, dilantin, asa
first-order
drugs are cleared at a rate proportional to the ant of drug in the plasma
most drugs
metabolism
biotransformation, to change active/lipid soluble drugs to water soluble and inactivate
vd is influenced by
lipid solubility
protein binding
molecular size
** only free drug have an effect on the body
lung uptake
with basic lipophillic drugs (lido, fentanyl, demerol) and acts as a resevior
distribution to cns
bbb prevents; ionized, water soluble wouldn’t cross
can be overcome with large doses/trauma
nonionized
lipid soluble
transdermal issues
sustained predictable conc
rate limiting step= diffusion stratum corneum epidermis; thickness and bloodflow to the area for skin permeability
contact dermatitis possible issue
pharmacokentics
what the body does to the drug
pharmacodynamics
what the drug does to the body
