pharmacokinetics part 1

Question 1

pharmacokinetics

Answer 1

what happens to the drug ie broken down

Question 2

the process of pharmcokinetics

4 answers

Answer 2

absorption
distribution
metabolism
excretion/ elimination

Question 3

factors affecting absorption

4 answers

Answer 3

lipid solubility
ionisation
formulation
gastro-intestinal function
first pass metabolism

Question 4

lipid solublility what does that entail

Answer 4

rapid from gut

slow form intra mascular

Question 5

ionisation what does this entail

Answer 5

poor for ionic drugs

ph partitioning

Question 6

formulation what does this entail

Answer 6

may limit the rate and extent of absorption

Question 7

gastro-intestinal function what does this entail

Answer 7

may limit rate of delivery to site of absorption
may limit availability for absorption
bacterial metabolism

Question 8

first pass metabolism what does this entail

Answer 8

may limit extent of absorption

does it get metabolised as soon as it gets to the liver

Question 9

ionisation of drugs

extent according to

Answer 9

pKa of drug

Ph of solution

Question 10

ionisation of drugs

for acids

Answer 10

low ph

conjurgate acid is lipid soluble

Question 11

ionisation of drugs

for bases

Answer 11

high pH

conjurgate base is lipid soluble

Question 12

ph partitioning what is it

Answer 12

concentration in the plasma over the stomach and urine

charged molecules cant cross membranes

Question 13

acid ionisation facts

Answer 13

most ionised at high ph
strong acids -pKa of less then 3
v.strong pKa of 1-2 poorly abosrbed

Question 14

bioavailability what is it

Answer 14

fraction of dose passing from site of administration into general circulation

Question 15

common reasons for low bioavailability

5 answers

Answer 15

decomposition in gut lumen
first pass metab in the gut wall
first pass metab in liver
not absorbed from gut lumen
tablet does not completely dissolve

Question 16

how do we measure bioavailability

Answer 16

compare the plasma concentration when the same dose is given iV and orally

Question 17

drugs affect first pass metabolism in the gut wall

inhibition of enzyme increases bioavailability but how does this eg

Answer 17

enzyme: MAO drug: amines inhibitor MAOI

if MAO is inhibited more tyramines is absorbed

Question 18

route of administration

oral what are the properties

Answer 18

DELAY
water soluble drugs absorbed slowly
lipid soluble drugs - absorbed rapidly

Question 19

distribution of drug

what happens if the membrane separates fluids at different ph values

Answer 19

drug will concentrate at the ph at which it is most ionised

Question 20

drug protein binding
reversible reactions for these drugs are
5 answers

Answer 20

non specific
low affinity
high capacity
saturate at high conc
not involved in drug activity

Question 21

drug protein binding also allows a

Answer 21

reserve of drugs

and can cause interactions with other ligands

Question 22

plasma albumin

Answer 22

binds to acidic and basic drugs

Question 23

drugs binding other drugs why does this occur

Answer 23

only important if the drug is highly protein bound

drug has a low vol of distribution

Question 24

drugs binding with endogenous compounds

why is this important

Answer 24

when they are highly bound its important

and they are active or toxic

Question 25

volume distribution depends on

Answer 25

total in tissue divided by

total in plasma

Question 26

if drug is held in plasma proteins it will

Answer 26

have a low vol distribution

Question 27

blood brain barrier

what does it provide

Answer 27

homeostatic mechanism allowing a constant cns environment

brain is not exposed to polar compounds

Question 28

parkinsons disease

what does dopamine have to do with it

Answer 28

dopamine cant cross the blood brain barrier
therefore carbidopa is used inhibits dopa decarboxylase
levodopa a precursor is left and can cross BBB

Question 29

rate of distribution depends on

Answer 29

diffusion rate of drug across membrane

and perfusion rate of tissue that take up drug

Question 30

factors affecting drug distribution

6 answers

Answer 30

rate - of partitioning into tissues
-cardiac output
extent- plasma binding protein
-synthesis (liver disease for albumin)
-synthesis (inflammatory disease from alpha 1)
-excretion (renal failure)

Question 31

route for drug elimination

Answer 31

volatile - exhailed
water soluble - urine
lipid soluble - metabolism