CAOP Drug Interactions and Contraindications 2

Question 1

A patient stabilised on lithium for bipolar disorder is prescribed naproxen for arthritis. What is the most likely outcome?

Accepted Answer

Lithium levels increase due to reduced renal prostaglandin-mediated excretion

Answer

NSAIDs reduce renal prostaglandin synthesis, decreasing renal blood flow and lithium excretion, which can increase lithium plasma levels into the toxic range.

Question 2

Beta-blockers are contraindicated in patients with which of the following respiratory conditions?

Accepted Answer

Reactive airway disease / bronchial asthma

Answer

Non-selective beta-blockers block beta-2 receptors in bronchial smooth muscle, causing bronchoconstriction and potentially fatal bronchospasm in asthmatic patients.

Question 3

Concomitant use of clopidogrel and omeprazole is clinically significant because:

Accepted Answer

Omeprazole inhibits CYP2C19, reducing conversion of clopidogrel to its active metabolite

Answer

Clopidogrel is a prodrug requiring CYP2C19 for activation; omeprazole's CYP2C19 inhibition reduces formation of the active thiol metabolite, diminishing antiplatelet efficacy.

Question 4

Oral tetracyclines should not be taken with dairy products because calcium:

Accepted Answer

Forms insoluble chelate complexes with tetracyclines, reducing absorption

Answer

Calcium (and other divalent/trivalent cations) chelates tetracyclines to form insoluble complexes in the gut, significantly reducing oral bioavailability by up to 50–80%.

Question 5

Oral fluoroquinolones (e.g., ciprofloxacin) should be administered at least 2 hours before or 6 hours after antacids primarily because antacids:

Accepted Answer

Chelate fluoroquinolones via magnesium/aluminium ions, reducing absorption

Answer

Magnesium and aluminium in antacids form insoluble chelate complexes with fluoroquinolones in the gastrointestinal tract, markedly reducing their oral absorption.

CAOP - Competency Assessment of Overseas Pharmacist Practice Test

CAOP - Competency Assessment of Overseas Pharmacist Practice Test

CAOP Drug Interactions and Contraindications 2