26. Pharmacokinetics: Drug Distribution, Metabolism and Elimination

Question 1

What is drug distribution?

Answer 1

Drug reversibly leaves blood stream and enters extracellular fluid and tissues

Question 2

What is the volume of distribution?

Vd

Answer 2

Therapeutic volume of fluid a drug would occupy if total amount of drug in body was in solution at same concentration as in plasma
Measure of tendency of a drug to leave the bloodstream
total amount of drug in body/plasma concentration

Question 3

What are 4 methods of excretion?

Answer 3

Renal
Billiary
Pulmonary Mammary

Question 4

What is first order elimination?

Answer 4

Constant fraction of a drug is eliminated

Rate is proportional to amount of drug

Question 5

What is zero order elimination?

Answer 5

Constant quantity is eliminated
Rate is independent of amount of drug
Eg. Ethanol

Question 6

What is the plasma half life?

Answer 6

Time taken for plasma to fall by 50%

Question 7

What does the plasma half life depend on?

Answer 7

Activity of metabolising enzymes

Distribution of blood into tissue

Question 8

What percentage has the concentration of the drug decreased by after 4 half lives?

Answer 8

94%