drug administration and elimination

Question 1

name some methods of administering drugs and their time to effect

Answer 1

Intravenous
30-60 seconds
Inhalation
2-3 minutes
Sublingual
3-5 minutes
Rectal
5-30 minutes
Intramuscular / subcutaneous
10-20 minutes
Oral
30-90 minutes

Question 2

what is the name of the cytochrome that partially metabolises drugs in the gut epithelium

Answer 2

CYP450 3A4

Question 3

what else partially metabolises drugs in teh GI tract

Answer 3

gut bacteria

Question 4

what is bioavailability

Answer 4

how much drug is available to be used systemically

Question 5

what is the BA of IV administered drugs

Answer 5

100%

Question 6

where is most BA lost in orally administered drugs

Answer 6

liver

Question 7

what is a prodrug

Answer 7

inactive drug that is metabolised to its active state

Question 8

what is L-Dopa

Answer 8

pro drug of dopamine

Question 9

how can prodrugs be used in cancer

Answer 9

antibody, gene or virus (ADEPT, GDEPT, VDEPT) delivered to cell. DNA expresses an enzyme
prodrug is administered
enzyme metabolises that cytotoxic drug and it sends the cells to apoptosis.
Bystander effect - nearby cells are also killed

Question 10

a patient has an adenocarcinoma of the lung. what is the most likely mutation

Answer 10

EGFR overexpression

Question 11

how would you use a prodrug to prevent tumour growth but not affect surrounding tissue

Answer 11

prodrug only binds to hypoxic tumour tissue

Question 12

which enzymes catalyse phase 1 of liver metabolism

Answer 12

CYP450

Question 13

what happens in phase 1

Answer 13

Oxidation
Reduction
Hydrolysis

Question 14

why would a molecule go to phase 2

Answer 14

too lipophilic

Question 15

what is the main mechanism in phase 2 and which molecule does it

Answer 15

glutathione conjugation - glutatione S-transferases

Question 16

why are adjuncts added to molecules in phase 2

Answer 16

to make them more polar = soluble

Question 17

what is carbemazepine

Answer 17

a CYP450 inducer epileptic drug

Question 18

which enzymes carry out oxidation, reduction, hydrolysis, conjugation, acetylation

Answer 18

O: CYP450 monooxygenazes
R: aldehyde and ketone reductases
H: esterases and amidases
C: gluathione S-transferases
Sulphotransferases
A: N-acetyl-transferase

Question 19

polar metabolites go to
non-polar metabolites go to

Answer 19

kidneys - wee
liver/GI - poooooooo

Question 20

how do you calculate clearance?

Answer 20

amount of drug lost in urine per hour/amount of drug remaining in plasma

Question 21

how do you calculate a half life

Answer 21

t1/2=(Vd/Cl) x 0.7

Question 22

for first order drugs, what should the dosing interval be

Answer 22

around 4(t1/2)

Question 23

what is the therapeutic window

Answer 23

a timeframe during which a drug is effective in the range between MEC and MSC

Question 24

what is succinylcholine used for

Answer 24

skeletal muscle paralysis during anaesthesia

Question 25

what does CYP 2D6 do

Answer 25

metabolises codeine into morphine plus beta blockers and tricyclic antidepressants

Question 26

what is the range of activity of CYP2D6 amongst different ethnicities

Answer 26

inactive in 7-8% of caucasians, only 1% Asians but hyperactive in 30% East Africans

Question 27

What is clopidogrel

Answer 27

anti-platelet