phamacokinteics 1

Question 1

what are the 5 pharmacokinetic parameters?

Answer 1

Liberation
Absorption
Distribution
Metabolism
Excretion

Question 2

what is the bioavalibity of a drug?

Answer 2

the fraction of unchanged drug which reaches systemic circulation (bioavilibity of IV drugs is 100%)

Question 3

what are the two main ways drugs can get across the cell membrane?

Answer 3

1. diffuse across the lipid bilayer (they need to be LIPOPHILIC to do this)
2. by transmembrane carrier proteins

Question 4

what are the two main properties of drugs which affect absorption?

Answer 4

lipophilicity and ionisation

Question 5

what internal chemical property affects ionisation?

Answer 5

pH

Question 6

what are six factors which affect drug distribution?

Answer 6

1. capillary permeability
2. plasma protein binding
3. pH of compartments
4. lipid solubility
5. degree of ionisation
6. cardiac output and blood flow

Question 7

what are some examples of important plasma proteins which drugs can bind to?

Answer 7

albumin
glycoproteins
lipoproteins
globulins

Question 8

what can cause a big increase in free drug availability?

Answer 8

competition for free binding sites on the plasma protein

Question 9

which drug also has a high affinity for albumin and so can therefore displace warfarin and increase the plasma concentration of warfarin?

Answer 9

aspirin

Question 10

which four factors influence a drugs distribution between body fluid compartments? (plasma water, interstitial water, fat, intracellular water, trans cellular water)

Answer 10

permeability across tissue barriers
binding within compartments
pH partition
fat:water partition

Question 11

how can distribution of drugs in different compartments be altered?

Answer 11

by changing their chemical structure (e.g. muscarinic antagonists and agonists)