Lecture 15

Question 1

Define drug clearance

Answer 1

The sum of all the drug-eliminating processes, principally determined by hepatic metabolism and renal excretion.

It can also be defined as the theoretical volume of fluid from which a drug is completely removed in a given period of time.

Question 2

What are the components of renal excretion

Answer 2

Glomerular filtration
Secretion
Reabsorption

Question 3

Apart from urine, what are other excretory methods

Answer 3

Bile (faeces); sweat; exhaled air; saliva; breast milk

Question 4

What is the role if the kidneys in drug clearance

Answer 4

Kidneys are the main drug excreting organ → Urine
Excretion unchanged
Metabolised then excreted

Question 5

What are the causes of low drug clearance

Answer 5

Normal variation
Renal impairment
Liver impairment
Enzyme inhibition
Genetic poor metaboliser
Neonate
Old age

Question 6

What are the causes of high drug clearance

Answer 6

Normal variation

Increased renal blood flow

Genetic hypermetabolism

Enzyme induction

Question 7

Define half life and what it provides information on

Answer 7

‘Time for the concentration of drug in plasma to halve’

Provides information on:
Time course of drug elimination
Time course of drug accumulation
Choice of dose interval

Question 8

Describe the dosing of drugs

Answer 8

half life )α Vd/Clearance

Loading dose is Determined by the volume of distribution

Maintenance dose is determined by the clearance

Dose interval is determined by the half life