Pharmacokinetics

Question 1

What is pharmacokinetics? [1 mark]

Answer 1

It is what the body does to the drug

Question 2

What is pharmacokinetics [1 mark]

Answer 2

It is what the drug does to the body

Question 3

What is absorption? [1 mark]

Answer 3

When an unchanged drug enters the circulation

Question 4

What is distribution? [1 mark]

Answer 4

Dispersion of a drug among fluids and tissues of the body

Question 5

What is metabolism? [1 mark]

Answer 5

Transformation of a drug into daughter compound(s)

Question 6

What is excretion? [1 mark]

Answer 6

Removal of drugs/metabolites from the body

Question 7

What is elimination? [2 marks]

Answer 7

Metabolism AND excretion

Question 8

Why is ADME important? [4 marks]

Answer 8

• Safe use
• Designing dose regimes
• Monitoring
• Medicinal licensing

Question 9

What is first pass metabolism? [2 marks]

Answer 9

• when the drug is funneled into the liver via the hepatic portal vein
• [drug] at systemic cirulation < [drug] absorbed

Question 10

Fick’s Law equation [4 marks]

Answer 10

Rate of diffusion = surface area x concentration gradient x permeability

Question 11

What happens to an acidic drug in acidic environments (e.g. stomach)? [1 mark]

Answer 11

More of it stays unionised/neutral

Question 12

What happens to an basic drug in basic environments (e.g. intestines)? [1 mark]

Answer 12

More of it stays unionised/neutral

Question 13

What is the Lipinski rule? [4 mark]

Answer 13

• Small molecular weight
• No more than 5 H-bond donors
• No more than 10 H-bond acceptors – related to metabolism
• Log P < 5 (partition coefficient)

Question 14

What can Lipinski minimise? [1 mark]

Answer 14

Desirable properties for receptor binding

Question 15

What is the half life and clearance for 1st order kinetics? [1 mark]

Answer 15

Constant

Question 16

What happens if you take a big dose in zero order kinetics? [1 mark]

Answer 16

The bigger the dose, the longer it takes to remove it

Question 17

What does the volume of distribution (Vd) show? [1 mark]

Answer 17

The extent of distribution

Question 18

Do drugs that bind tightly to plasma proteins have a higher or lower Vd? [2 marks]

Answer 18

LOWER

- ‘trapped’ in the circulation

Question 19

What is clearance (CL)? [2 marks]

Answer 19

• The volume of blood cleared of the drug per time

- Higher CL = lower half time

Question 20

What does bioavailability measure? [1 mark]

Answer 20

The extent of absorption

Question 21

What is the steady/plateu state? [1 mark]

Answer 21

Where:

[drug] absorbed = [drug] eliminated

Question 22

How can the attainment of steady state be accelearated? [2 marks]

Answer 22

• By an initial loading dose

- Followed by a maintenance dose

Question 23

How are drugs metabolised? [1 mark]

Answer 23

They are made water soluble

Question 24

What are the 2 phases of drug metabolism? [2 marks]

Answer 24

• Introducing chemically reactive groups

- Increasing water solubility for excretion

Question 25

How are chemically reactive groups introduced to drugs? []

Answer 25

• Oxidation in liver

- Done by CYP450

Question 26

What is an example of a drug that skips the first phase of drug metabolism? [1 marks]

Answer 26

Paracetamol

Question 27

Excretion equation

Answer 27

Excretion = filtration (via glomerulus) - reabsorption (via loop of Henle) + secretion (plasma protein releases drug)

Question 28

What does a lower renal clearance result in? [1 mark]

Answer 28

Higher plasma half life of drug

Question 29

Factors that affect drug metabolism & excretion [4 marks]

Answer 29

• Age
• Genetics
• Drug metabolising enzymes
• Disease