Drug elimination Flashcards
principle organ for drug elimination
kidneys
what is drug elimination mostly accomplished by
renal filtration of blood plasma
what are water and most electrolytes reabsorbed into
blood circulation in the renal tubules
what are not reabsorbed and instead excreted in urine
drug metabolites rendered polar by phase 2
clearance
elimination of a drug form the body
volume of blood removed of drug per unit of time
what can clearance be broken down into
renal, hepatic, other or total clearanceqh
why is clearance important
helps determine dosage rate needed to maintain a desired plasma
what is cl indeendant of
dv but both determine elimination half life of a drug
clearance calc
rate of drug elimination/ drug plasma
vmax
maximal elimination rate
first order kinetics
rate of drug elimination increasees as plasma drug conc increases
zero order kinetics
elimination reaches max
Michaelis menten kinetics
re = vmax x drug plasma/ km + drug plasma
km
drug concentration at which rate of elimination is 1/2 vmax
drug plasma
drug concentration in plasma
steady state
rate of drug administration = drug elimination
dosage rate calc
drug plasma x cl
elimination half life - t1/2
determines the time required for drug plasma to achieve drug plasma ss and how much time is required for drug to be eliminated from body
elimination half life calc
0.693 x vd/ cl
how many half lives are required to reach steady state
5
determinants of t1/2
cl increases, t1/2 decreases
cl decreases t/12 increases
vd increases, t1/2 increases
vd decreases t/12 decreases
effects on volume of distribtuon
aging, decreases t1/2 due to decrease in muscle mass
obesity; t/12 increases
pathologic fluid increases t1/2
