SL011 Elimination Lectures Flashcards
(21 cards)
State the equation for the rate of renal elimination
Rate of renal elimination = Renal clearance*Cdrug
What’s the difference between clearance and elimination rate?
Clearance refers to the amount of fluid being cleared of drug whereas the elimination rate refers to the mass of drug being eliminated.
Define elimination
The irreversible loss of drug by excretion and/or metabolism
Define excretion
Irreversible loss of chemically unchanged drug.
Why doesn’t excretion apply to chemically changed drug?
If its already been chemically altered then it has been metabolised and therefore already eliminated so it isn’t counted.
Define metabolism (as it refers to elimination)
Conversion of the drug into a different chemical species.
What is another term for metabolic elimination?
Biotransformation
In what organs are drugs eliminated by metabolic activity? Which organ primarily carries out this role?
Mainly the liver
Lungs
GI wall
Blood
Skin
Kidneys
Rate of elimination equation
Rate of elimination = Clearance*Cdrug
How do you determine clearance from a rate of elimination/Cp graph?
The gradient of the plotted line will be the clearance
Define clearance
The capacity of the body to eliminate the drug
Define elimination rate
The rate at which a drug is eliminated from the body
How will the plasma profiles of two drugs differ if one has a greater clearance?
The one with the greater clearance will have its plasma levels decay faster
What is a plasma profile? Why do we use them?
A graph of the plasma concentration of a drug against time. They can be used to compare the decay of different drugs in the plasma.
What conditions are required for the steady state? Define this as an equation.
The rate of drug into the body is equal to the rate of drug out of the body.
Rate in = Rate out
Steady state equation
Rate in (dose/time) = Rate out (Cl*Css)
What does Css stand for
The steady state concentration
Why is the steady state so important for dosing regimens?
By achieving a steady state, we can maintain a plasma concentration of a drug, thus keeping it within a therapeutic range.
What clearance is not additive? Why?
Lung clearance. This is because blood does not pass through the lungs just once and the manner by which it does so is not straight forward.
Additive clearance equation
Total Cl = Renal Cl + Hepatic Cl + SUM(Tissue Cl)
