Introduction to Pharmacokinetics

Question 1

What is pharmacokinetics?

Answer 1

Getting drugs to and from their site of action

Question 2

What are the four steps of pharmacokinetics?

Answer 2

drug administration, drug absorption, drug distribution, drug elimination (metabolism and excretion)

Question 3

What factors influence route of administration?

Answer 3

convenience, cost, bioavailability, whether you need a local or systemic effect

Question 4

What factors influence distribution?

Answer 4

molecular size, ability to bind plasma proteins, lipid solubility

Question 5

What are drug reservoirs?

Answer 5

Sites in the body where a drug can accumulate

Question 6

What is volume of distribution?

Answer 6

Vd = X/C where X is amount of drug in body and C is concentration in plasma

Question 7

What are the two forms of drug elimination?

Answer 7

excretion - in the kidney and metabolism in the liver

Question 8

What are the steps in renal excretion?

Answer 8

glomerular filtration, tubular secretion (active), tubular reabsorption

Question 9

What is the relationship between pH and lipid solubility?

Answer 9

acidic drugs are lipid soluble in low pH, basic drugs are lipid soluble in high pH

Question 10

What is renal clearance?

Answer 10

glomerular filtration + tubular secretion - tubular reabsorption

Question 11

When is an acidic drug more lipid soluble?

Answer 11

in low pH solutions

Question 12

What is a basic drug more lipid soluble?

Answer 12

in high pH solutions

Question 13

How do you treat aspirin overdose?

Answer 13

With sodium bicarbonate - because aspirin is an acidic drug a basic solution will make it less lipid soluble so it will not be reabsorbed and therefore will be excreted

Question 14

What is renal clearance?

Answer 14

the amount of blood from which the drug is removed by the kidneys per time

Question 15

What is the maximum renal clearance?

Answer 15

800mL/min (i.e. renal blood flow)

Question 16

What is drug metabolism?

Answer 16

a chemical change to a drug

Question 17

What is the main site of drug metabolism?

Answer 17

the liver

Question 18

What is the main outcome of drug metabolism?

Answer 18

increase the water solubility and decrease the lipid solubility of a drug so that it can be excreted

Question 19

What are the different types of metabolites that can be formed?

Answer 19

inactive, active in the same way as the parent compound, active in a different way to the parent compound, or toxic

Question 20

What is phase I metabolism?

Answer 20

a reaction which creates a chemical functional group on a drug that it didn’t have before

Question 21

What is phase II metabolism?

Answer 21

conjugation of a water soluble molecule to a functional group on a drug

Question 22

What is the usual outcome of a metabolite from phase II metabolism?

Answer 22

it is inactive

Question 23

Do phase I and phase II metabolism both have to happen?

Answer 23

No - can have just one of either or both