15.10 Pharmacology: Advanced Pharmacokinetics

Question 1

What are the following terms called?:
Giving the drug
Drug entering circulation
Drug spreads through the body
Drug removal from the body

Answer 1

Administration
Absoption
Distribution
Elimination (chemical: metabolism, physical: excretion)

Question 2

What is the use of the liver converting things into metabolites?

Answer 2

More water soluble so able to be excreted

Question 3

What does the ‘clearance’=?

Answer 3

=extraction ratio x blood flow

Question 4

What is renal clearance?

Answer 4

Amount of blood from which drug is removed by kidneys/time

Question 5

What is maximal GFR and maximal CLrenal?

Answer 5

GFR: 120mL/min
CLrenal: 800mL/min

Question 6

What is the equation for the CLtotal?

Answer 6

CLtotal= CLrenal + CLhepatic +CLother

Question 7

What does renal excretion/drug metabolism depend on?

Answer 7

Concentration on drug in blood

Question 8

Most drugs distribute…..

Answer 8

Rapidly

Question 9

Most drugs are eliminated at a rate proportional to….

Answer 9

concentration in plasma (first order kinetics)

Question 10

The amount of drug in the body falls……… …. ….. (first order elimination-IV)

Answer 10

The amount of drug in the body falls exponentially with time

Question 11

What are the features of rapid IV administration (first order elimination) ? (3)

Answer 11

Rapid rise in body
Drug has half life
Peak concentration related to dose

Question 12

What does the curve for a short term IV infusion look like?

Answer 12

Like a wave

Question 13

What are features of short term iv infusion? (3)

Answer 13

Rate of accumulation decreases as concentration increases
Peak not as high as IV bolus
After infusion is over, get elimination only (simple first order)

Question 14

What is short term iv infusion useful for?

Answer 14

For drugs with a narrow therapeutic window, e.g. gentamycin

Question 15

What are the features of long term IV infusion (one compartment model, first order elimination)? (2)

Answer 15

• At steady state, rate of infusion=rate of elimination

- Css is proportional to infusion rate (easy to dial up to a particular concentration)

Question 16

What happens in multiple dosing?

Answer 16

Trough will be half of the peak (if drug is given every half life): 2 fold variation to steady state

Question 17

What is a loading dose?

Answer 17

We avoid lag time by bringing concentration up and then maintaining it (quicker)

Question 18

How does absorption following oral administration take place primarily?

Answer 18

Via lipid diffusion

Question 19

What is first pass hepatic metabolism?

Answer 19

Following oral administration, drug enters hepatic portal vein and is transferred directly to the liver

Question 20

What are the features of oral administration (first order elimination)? (2)

Answer 20

Peak not as high as with IV

Not all of drug may be absorbed, some may undergo first pass metabolism

Question 21

What does bio availability mean?

Answer 21

Proportion of active drug which enters systemic circulation (need to take this into account when calculating dose, administer more if low bio availability)