2) Pharmacokinetics

Question 1

Define pharmacokinetics:

Answer 1

Movement of drug into and out of the body

Question 2

Define pharmacodynamics:

Answer 2

Drug effect and mechanism of action

Question 3

Define pharmacogenetics:

Answer 3

Effect of genetic variability on pharmacokinetics or dynamics of drug

Question 4

Describe the processes a drug goes under when it enters the body:

Answer 4

Absorption, distribution, metabolism, elimination

Question 5

What is bioavailability?

Answer 5

Fraction of a dose that finds its way into a body compartment

Question 6

What is the equation for bioavailability?

Answer 6

amount of drug reaching circulation/total drug administered

Question 7

What factors affect the absorption of a drug?

Answer 7

Formulation
Age
Lipid or water soluble
Vomiting/malabsorption

Question 8

What two factors affect bioavailability?

Answer 8

Absorption

First pass metabolism

Question 9

What is first pass metabolism?

Answer 9

Any metabolism occurring before the drug enters systemic circulation
Occurs in gut lumen, gut wall and liver

Question 10

What factors affect the distribution of a drug?

Answer 10

Protein binding

Volume of distribution

Question 11

What proteins do drugs commonly bind to?

Answer 11

Albumin, globulins, lipoproteins and acid glycoproteins

Question 12

When are protein binding drug interactions important?

Answer 12

If drug has high protein binding
Low volume of distribution
Narrow therapeutic window

Question 13

What factors affect protein binding?

Answer 13

Hypoalbuminemia
Pregnancy
Renal failure
Displacement by other drugs

Question 14

What is the volume of distribution?

Answer 14

Measure of how widely a drug is distributed in body tissues

Question 15

What is the equation for calculating volume of distribution?

Answer 15

dose/conc of drug at T0

Question 16

Give examples of drugs with a low volume of distribution:

Answer 16

Furosemide, warfarin

Question 17

Give examples of drugs with a high volume of distribution:

Answer 17

Amiloride, digoxin

Question 18

What are pro-drugs? Give an example:

Answer 18

Inactive until metabolism

L-DOPA

Question 19

How is the action of cytochrome p450 influenced?

Answer 19

By inducers and inhibitors

Age, liver disease, hepatic blood flow, smoking and alcohol

Question 20

Give examples of CYP450 isoenzymes:

Answer 20

CYP 2D6, 2C9, 2C19, 3A4

Question 21

How does CYP2D6 vary in different populations?

Answer 21

Absent in 7% of Caucasians

Hyperactive in 30% of East Africans

Question 22

What are the routes of elimination for a drug?

Answer 22

Kidneys, lungs, sweat and bile

Question 23

What 3 processes determine the overall renal excretion of a drug?

Answer 23

GFR
Passive tubular reabsorption
Active tubular secretion

Question 24

What is clearance?

Answer 24

Ability of body to excrete drug

Question 25

Define 1st order kinetics in regard to drug elimination:

Answer 25

Rate of elimination proportional to drug level, half life defined

Question 26

Define zero order kinetics in regard to drug elimination:

Answer 26

Rate of elimination is constant

Question 27

How is half life calculated?

Answer 27

(0.693 x Vd)/Clearance

Question 28

When should drugs be monitored?

Answer 28

Zero order, long half life, narrow therapeutic window, risk of drug-drug interactions, known toxic effects

Question 29

What factors affect clearance?

Answer 29

Heart - blood flow to liver and kidneys

Renal and hepatic diseases