Common Drug-Drug interactions

Question 1

Amiodarone + Warfarin

Answer 1

2C9 = increased warfarin levels

Question 2

carbamazepine or phenobarbital or phenytoin + Ethinyl estradiol contraceptives

Answer 2

3A4 = reduced contraception

Question 3

clarithromycin or erythromycin or telithromycin + simvastatin or verapamil

Answer 3

3A4 = increased simvastatin or verapamil levels thus myopathy/rhabdomyolysis or QT prolongation/hypotension respectively

Question 4

diltiazem or verapamil + prednisone

Answer 4

3A4 = increased prednisolone levels thus immunosuppression

Question 5

fluoxetine or paroxetine + risperidone or tramadol

Answer 5

2D6 = increased risperidone or decreased active metabolites of tramadol

Question 6

grapefruit juice + buspirone

Answer 6

3A4 = increased buspirone thus dizziness

Question 7

metronidazole + warfarin

Answer 7

2C9 = increased warfarin levels

Question 8

terbinafine + amitriptyline

Answer 8

2D6 = prolonged increase in amitriptyline thus dry mouth, dizziness and cardiac toxicity