Drug Clearance Flashcards
What is clearance?
Volume of plasma cleared entirely of drug per unit time
What is the unit of clearance?
mL/min or L/hr
Relationship between clearance and elimination rate
Elimination rate = clearance * plasma concentration
Amount of drug in body (mg) =
Volume (litres) x concentration (mg/L)
What is clearance total equation?
Clearance (hepatic) + clearance (renal) + clearance (other)
What is the equation for initial concentration (mg/ml)?
Dose mg/ volume L
What is the equation of concentration at time (t)?
Initial concentration * e (-cl/v t)
What is the half life equation?
In(2)V/Cl
What is the In(2) =
0.693
How do you work out the concentration of a steady rate constant infusion?
Concentration = infusion rate / CL
When is clearance constant?
Only constant if the elimination process isn’t saturated
What processes contribute to total body clearance of a drug?
Hepatic metabolism and excretion, renal, gut, tears, sweat, breath and breast milk
What is the two variables that contribute to the clearance?
Rate of elimination
Drug concentration in the plasma
What biological processes are concentration dependent?
diffusion, enzyme mediated metabolism.
Clearance?
Rate of elimination / concentration
