The kidney and excretion Flashcards
what is excretion?
the process the removes the drug, or its metabolites, from the body. Principally by the kidneys, renal excretion, but other routes may be important for specific agents.
what is elimination?
the linked process of metabolism and excretion
what is pharmacokinetics?
is the mathematical analysis of all drug disposition factors (absorption, distribution, metabolism and excretion)
what does it mean if a drug exhibits first order kinetics?
drug elimination is directly proportional to drug conc.
what is clearance?
the volume of plasma cleared of drug in unit time.
clearance is a constant that relates what two things?
the rate of elimination to plasma concentration.
clearance determines what?
the maintenance dose rate
what is the maintenance dose rate?
dose per unit time to maintain a given plasma concentration
clearance is only applied to drugs that exhibit what?
first order kinetics
what does it mean to reach steady state?
rate of drug administration = rate of drug elimination
what is the volume of distribution?
the volume into which a drug appears to be distributed with a concentration equal to that of plasma
volume of distribution is a proportionality constant relating what two things?
the plasma concentration to the amount of drug in the body
put these into an equation
volume of distribution
plasma concentration
amount of drug in the body
amount of drug in the body = volume of distribution x plasma concentration
what can change the volume of distribution?
disease so adjust dose, especially drugs with a low therapeutic range
what is loading dose?
initial higher dose of a drug at the start of treatment before stepping down to a lower maintenance dose
what is loading dose used for?
reduce the time take to reach the steady state for drugs with long half life’s
what is half life for a drug?
time for the amount of drug in the body to halve
half life is proportional to what?
volume of distribution / clearance
what does it mean if a drug has zero order?
drugs are eliminated at a constant rate
drugs are eliminated in the urine by what?
glomerular filtration
what is glomerula filtration rate?
test to show how well the kidneys are working by estimating how much blood passes through the glomeruli every minute.
what are glomeruli?
tiny filters in the kidney which filter waste from blood
what is a normal glomerular filtration rate?
90ml/minute or higher
what is the glomerular rate for mild renal failure / stage 2?
60-89ml/minute
