CAOP Drug Interactions and Contraindications

Question 1

A patient on warfarin is prescribed ibuprofen for pain. What is the primary concern with this combination?

Accepted Answer

Increased bleeding risk due to additive anticoagulation and GI mucosal damage

Answer

Reduced anticoagulant effect of warfarin

Answer

Ibuprofen accelerates warfarin metabolism via CYP2C9 induction

Answer

Warfarin increases ibuprofen plasma levels causing toxicity

Question 2

Which combination of antihypertensive agents poses the greatest risk of dangerous hyperkalaemia?

Accepted Answer

ACE inhibitor + potassium-sparing diuretic

Answer

ACE inhibitor + calcium channel blocker

Answer

Beta-blocker + thiazide diuretic

Answer

ARB + calcium channel blocker

Question 3

A patient taking a monoamine oxidase inhibitor (MAOI) is started on sertraline. What potentially fatal interaction can occur?

Accepted Answer

Serotonin syndrome due to excessive serotonergic activity

Answer

Hypertensive crisis due to norepinephrine accumulation

Answer

Neuroleptic malignant syndrome due to dopamine blockade

Answer

Severe anticholinergic toxidrome

Question 4

Amiodarone is added to a patient's regimen that includes digoxin. What is the expected pharmacokinetic outcome?

Accepted Answer

Amiodarone inhibits P-glycoprotein and CYP, increasing digoxin plasma levels

Answer

Amiodarone induces P-glycoprotein, reducing digoxin levels

Answer

Digoxin inhibits amiodarone metabolism, causing amiodarone toxicity

Answer

No clinically significant interaction between these two agents

Question 5

Metformin should be withheld before and after administration of iodinated contrast media primarily because of the risk of:

Accepted Answer

Contrast-induced nephropathy leading to metformin accumulation and lactic acidosis

Answer

Hypoglycaemia due to altered carbohydrate metabolism

Answer

Allergic cross-reaction between metformin and iodine

Answer

QT prolongation due to the combination

Question 6

Concomitant use of a statin and gemfibrozil significantly increases the risk of:

Accepted Answer

Rhabdomyolysis due to increased statin plasma concentrations

Answer

Hepatotoxicity leading to fulminant hepatic failure

Answer

Severe hypoglycaemia by inhibiting gluconeogenesis

Answer

Prolonged QT interval and torsades de pointes

Question 7

Which of the following medications is most commonly associated with QT interval prolongation and torsades de pointes when combined with other QT-prolonging agents?

Accepted Answer

Domperidone

Answer

Metoprolol

Answer

Omeprazole

Answer

Metformin