DRUGS

Question 1

what is the effect of an enzyme inducer?

Answer 1

increases cytochrome P450 enzyme activity, hastening the metabolism of other drugs

makes other drugs less effective as they are metabolised quicker. Therefore other drugs may require a dose increase

Question 2

what is the effect of an enzyme inhibitor?

Answer 2

decreases cytochrome P450 enzyme activity, meaning there will be increased levels of other drugs

increases the effectiveness of other drugs as they are metabolised slower so have higher concentrations in the body. Therefore other drugs may require a dose reduction.

Question 3

what are the most common enzyme inducers?

Answer 3

CRAP GPS

• carbamazepine
• rifampicin
  Alcohol (chronic excess)
• Phenytoin
• Griseofulvin
• Phenobarbitone
• Sulfonylureas (gliclazide)
• Smoking
• St johns wort

Question 4

what are the most common enzyme inhibitors?

Answer 4

SICKFACES.COM
- sodium valproate
- isoniazid
- cimetidine
- ketoconazole
- fluconazole
- acute alcohol (+grapefruit juice), allopurinol, amiodarone
- chloramphenicol
- erythromycin
- sulphonamides, Sertraline
- ciprofloxacin
- omeprazole
- metronidazole

Question 5

what is the effect of adding an enzyme inhibitor in patients taking warfarin?

Answer 5

• causes rise in INR (are excessively anticoagulated)
• warfarin dose needs reducing

Question 6

how are topical drugs commonly prescribed?

Answer 6

in fingertip units (FTUs)

1 FTU = from tip of adult finger to first crease

it provides enough to treat one side of both hands

Question 7

which drugs can cause lung fibrosis?

Answer 7

amiodarone
cytotoxic agents
methotrexate, sulfasalazine
nitrofurantoin
dopamine receptor agonists (bromocriptine, cabergoline, pergolide)

Question 8

which drugs can cause urinary retention?

Answer 8

TCAs (amitriptyline)
anticholinergics
opioids
NSAIDs
disopyramide