Pharmacokinetics

Question 1

What property of drugs allows them to cross the blood brain barrier?

Answer 1

Lipid solubility

Question 2

What is bioavailability?

Answer 2

Percentage of drug that reaches systemic circulation

Question 3

What is the bioavailability when a drug is given IV?

Answer 3

100%

Question 4

What is distribution?

Answer 4

How far the drug has spread

Question 5

What is the equation for distribution?

Answer 5

Dose = volume distribution x plasma concentration

Question 6

What does a distribution of 3L mean?

Answer 6

Drug has spread throughout plasma e.g. antibody

Question 7

What does a distribution of 42L mean?

Answer 7

Drug spread through total body water (e.g. very small/lipophilic)

Question 8

What does a distribution of 6L mean?

Answer 8

Drug spread through blood

Question 9

What would a very high distribution indicate?

Answer 9

Drug is bound to tissues

Question 10

What type of drugs accumulate in renal failure?

Answer 10

Water soluble drugs e.g. digoxin, metformin

Question 11

What are CYPs?

Answer 11

Molecules in the liver responsible for metabolism

Question 12

What drugs induce CYPs, therefore increasing breakdown of drugs?

Answer 12

St Johns Wort
Barbiturates
EtOH
AEDs
Rifampicin

Question 13

What drugs inhibit CYPs, therefore reducing breakdown of drugs?

Answer 13

Grapefruit juice
Antibiotics
Antifungals - ketoconazole
Amiodarone

Question 14

Which antibiotics are CYP inhibitors?

Answer 14

Macrolides
Metronidazole
Quinolones
Chloramphenicol
Clarithromycin

Question 15

What drugs are affected by CYPs i.e. substrates?

Answer 15

Warfarin
Phenytoin
Theophylline
OCP
Ciclosporin

Question 16

What can cause long half life?

Answer 16

Low clearance

High volume of distribution