pharmacokinetics

Question 1

DEFINE: pharmacokinetics

Answer 1

study of the absorption, distribution, metabolism and excretion of drugs from the body

Question 2

DEFINE: pinocytosis

Answer 2

plasma membrane invaginating extracellular fluid and absorbing it

Question 3

what is the intrathecal route of drug administration?

Answer 3

drug administered into CSF + enters brain

used for drugs acting on CNS

Question 4

what is the diffusivity diffusion coefficient?

Answer 4

how rapidly the drug moves between the lipids

larger molecular weight = slower to equilibriate in lipids

Question 5

how does the ability of a drug to partition into specific tissues e.g. fat affect drug absorption?

Answer 5

will remain in the body for longer so action of drug is extended

Question 6

what are the 2 biochemical reactions occurring in the liver when a drug is metabolised?

Answer 6

1. catabolic reaction producing a more reactive compound

2. synthetic anabolic reaction - involves conjugation to produce inactive product

Question 7

what are pro-drugs?

Answer 7

drugs that only become active after they are metabolised

Question 8

p450 enzymes

Answer 8

found in ER membranes within liver cells

use haem group to oxidise molecules (either add or unmask a polar group) making them more water-soluble for clearance

Question 9

why are some drugs excreted via faeces

Answer 9

• orally ingested, unabsorbed drug

- metabolites excreted in bile

Question 10

how does pH affect the movement of drugs through membranes (weak acids)

Answer 10

high pH –> acid dissociation. weak acid becomes ionised + cannot diffuse across membranes
low pH –> weak acid unionised + can diffuse more readily