Drug Clearance Flashcards
Define drug clearance
Volume of plasma cleared entirely of drug per unit time
Units of drug clearance
mL /min or L /hr
Drug clearance is a constant proportionally between?
Rate of elimination and the plasma concentration
If 25% of plasma flowing through the kidney (approx. 1L /min ) is cleared of drug. What is the clearance?
250 mL/ min
Elimination rate =
EQUATION
Clearance x plasma concentration
Clearance is ?/?
EQUATION
Volume / time
Plasma concentration is ?
EQUATION
Mass / volume
Elimination= ?/?
EQUATION
Mass / time
Equation: clearance total =
CL hepatic + CL renal + CL other
If 1/3 of the drug is eliminated through the kidneys then you can describe it as having a significant renal elimination route. Why is that Important?
need to know how a drug is cleared, so you know it is set to be given through that route
Equation: Amount in body mg =
Volume, L x concentration, mg/L
Half life equation
= ln (2) V / CL
Initial concentration mg/L =
EQUATION
Dose mg/ volume L
Concentration at time t=
EQUATION
Initial concentration x e^ -CL/V ^t
Calculation for constant rate infusion at steady rate, concentration =
Infusion rate / CL
Clearance is only constant it?
The elimination process isn’t saturated
Calculation for clearance in kinetic graph ( rate of elimination plotted against drug concentration in plasma)
Clearance= rate of elimination / concentration
In first order kinetics describe graph for clearance
Constant line up
Rate of elimination is proportional to drug concentration in plasma
Higher drug concentration, higher the elimination rate
In zero order kinetics describe graph for clearance
Rate of elimination reaches a plateau as drug concentration in plasma increases
Zero order elimination rate is independent of concentration
Alcohol is an example that shows what order of kinetics for clearance
Zero
