F2 ADME & clinical pharmacology 2

Question 1

Define a drug interaction

Answer 1

occur when the effects of one drug are changed by the presence of another drug, food, drink, or an environmental chemical agent
cause increase toxicity or reduce activity

Question 2

How does pharmacokinetic mechanisms be effected by absorption and pH?

Answer 2

absorption - 2 drugs may interact to alter rate of uptake

pH: rise in pH may influence absorption of other drugs

Question 3

What does MDR1 stand for?

Answer 3

multiple drug resistance

Question 4

Define efflux

Answer 4

pumps drug out into lumen

Question 5

What does metoclopramide accelerate?

Answer 5

absorption of other drugs

Question 6

What is meant by isoenzymes with reference to cytochrome P450

Answer 6

variety of the enzyme P450

Question 7

what is enzyme induction?

Answer 7

increase activity of metabolising enzymes

Question 8

Which causes enzyme induction?

Answer 8

barbiturates 
rifampicin - anti TB drug 
griseofulvin 
phenytoin - anti- epileptic 
ethanol 
carbamazepine anti epileptic 
St John's Wort

Question 9

Which drugs does rifampicin increase metabolism of?

Answer 9

oral contraceptives

Question 10

What causes Cytochrome P450 inhibition?

Answer 10

cimetidine 
antifungal agents 
erythromycin/ clarithromycin 
ciclosporin 
Psoralen

Question 11

What effects on metabolism do metoprolol, codeine and tamoxifen have?

Answer 11

metoprolol - enhanced action in poor metabolisers
codeine - requires metabolic conversion so reduced response in poor metabolisers
tamoxifen - in poor metabolisers impaired conversion to active antagonist and impaired survival in great cancer

Question 12

How does omeprazole make clopidogrel less effective?

Answer 12

both biotransferred to cyt P450 so clopidogrel is no longer converted to active metabolite