Lecture 2. Pharmacokinetics 2

Question 1

What does IV bolus mean?

Answer 1

100% drug given all at once

Question 2

What is the apparent volume of distribution (Vd)?

Answer 2

Amount in body at equilibrium / Plasma drug concentration

Question 3

What causes a low apparent volume of distribution?

Answer 3

Low lipid solubility + low tissue binding

Question 4

What causes a high apparent volume of distribution?

Answer 4

High lipid solubility + High tissue binding

Question 5

What is clearance?

Answer 5

Rate of elimination / concentration of input

Question 6

What are the units of clearance?

Answer 6

Volume/time (ml/min)

Question 7

What is the total body clearance?

Answer 7

The sum of all the clearances occuring simultaneously by different organs in the body

Question 8

Where is clearance frequently measured?

Answer 8

Hospitals

Question 9

Why is creatine used to measure clearance rate instead of inulin?

Answer 9

Only one blood sample is needed to measure clearance with creatine

Question 10

How to calculate creatine clearance?

Answer 10

Rate of production / serum creatine

Question 11

What are the two ways to measure clearance?

Answer 11

Single blood sample and/or renal clearance: uring collection over 24 hours

Question 12

What is the normal creatine clearance for healthy women?

Answer 12

88-128ml/min

Question 13

What is the normal creatine clearance for healthy men?

Answer 13

97-137ml/min

Question 14

Does clearance increase or decrease with age?

Answer 14

Decrease

Question 15

What is first order elimination kinetics?

Answer 15

Rate of elimination is proportional to drug concentration

Question 16

What is elimination rate constant (Kel)?

Answer 16

Proportion of drug eliminated per unit time (min⁻ ¹)

Question 17

What is the time constant?

Answer 17

1/Kel

Question 18

If you plot a natural log of concentration graph against time, what is the gradient?

Answer 18

-Kel

Question 19

What is the half life?

Answer 19

The time taken for the drug concentration to fall by half

Question 20

How do you calculate half life?

Answer 20

ln2/Kel

Question 21

What can half-life help determine?

Answer 21

The dosing interval

Question 22

What is the rate of absorption proportional to?

Answer 22

The amount of drug unabsorbed
The more drug you have, the more drug is absorbed

Question 23

What does the area under the curve measure?

Answer 23

The amount of drug absorbed

Question 24

How can bioavailability be calculated from areas under the curve?

Answer 24

AUC dosage form / AUC IV injection

Question 25

What are the properties of a loading dose?

Answer 25

Acute conditions
Status asthamticus
Status epilepticus
Long elimination half life

Question 26

What happens during a continuous infusion?

Answer 26

Slowly build up drug concentration over time

Question 27

What is zero order kinetics also known as?

Answer 27

Saturation kinetics

Question 28

What does zero order kinetics mean?

Answer 28

Rate of elimination is not proportional to drug concentration but is constant

Question 29

What are examples of substances that follow zero order kinetics?

Answer 29

Ethanol, phenytoin

Question 30

Is there any change in absorption with age?

Answer 30

Little change

Question 31

Why can therapeutic drug monitoring be used for?

Answer 31

Measuring the concentration of drug in the body
To determine the most effective dose or to avoid toxicity
Can measure drug in blood, urine (or saliva if unbound)

Question 32

What is the use of urine sampling?

Answer 32

Useful as do not need blood sample
Useful for drugs which are fully/partially eliminated in the urine
Volume of urine is very variable so do not use drug concentration
Express quantity of drug as absolute amount

Question 33

What is a disadvantage of urine sampling?

Answer 33

Drug must be excreted via kidneys

Question 34

How can a drug be measure if it has been metabolised?

Answer 34

Measure the metabolite