Quantitative pharmacokinetics

Question 1

Glomerular filtrate rate

Answer 1

125ml/min

Question 2

If renal CL of drug = 125ml/min drug is…

Answer 2

filtered only

filtered and secreted, but reabsorbed to same extent as secretion

Question 3

If renal CL of drug < 125 ml/min drug is…

Answer 3

Filtered + absorbed

Question 4

If renal CL of drug > 125 ml/min drug is…

Answer 4

Filtered + secreted

Question 5

How does I.V. infusion counter rate of elimination

Answer 5

Concentration in Vd will increase, until a concentration is reached where rate of elimination = rate of infusion.

Question 6

Calculate infusion rate

Answer 6

Infusion rate = Css × CL

• steady state reached after 4 half-times
• steady state con depends on infusion rate + clearance

Question 7

steady state conc depends on

Answer 7

infusion rate + clearance

Question 8

Time to peak (tmax) depends on…

Answer 8

rate of absorption

Question 9

Bioavailability

Answer 9

Measure of total drug absorbed

AUC oral/ AUC iv

Question 10

How do we aim to keep dose within large therapeutic window

Answer 10

Maximal dose strategy

Question 11

How do we aim to keep dose within narrow therapeutic window

Answer 11

Target level strategy

Question 12

How do we speed up time to Css

Answer 12

Loading dose

Question 13

Variation in pharmacokinetics parameters between ppatients

Answer 13

Normal genetic variation in expression of proteins involved in uptake, metabolism and secretion of drugs
Variation in volume of distribution
Variation in pharmacodynamics
Drug-drug interactions (+ food constituents)
Age