Lecture 3

Question 1

What’s the equation for the elimination rate?

Answer 1

Clearance (L/h) x concentration (mg/L)

Question 2

How are drugs eliminated?

Answer 2

Liver - by metabolism and biliary excretion 
Kidneys - 
Ionised 
Hydrophilic 
Small 

Non-ionised drugs and lipophilic drugs are reabsorbed and go to the liver where they are made more lipophilic and get excreted.

Question 3

What is the maintenance dose?

Answer 3

Dose rate to achieve a target concentration - the steady state concentration, where the dose rate in = rate of elimination.

MD = clearance (L/h) x target concentration (mg/L)

Question 4

What does a constant clearance classification mean?

Answer 4

It means that it is independent of the blood flow and concentration.

First order or linear elimination

Question 5

What does a concentration dependent clearance mean?

Answer 5

Clearance changes with concentration - mixed order or non-linear elimination.

Its concentration independent at low concentrations but as the concentration increases it becomes concentration dependent as the metabolising enzymes