APC APC Drug Interactions and Contraindications 1 — Questions and Answers
Question 1: Which combination is a well-known clinically significant drug interaction that can increase the risk of serotonin syndrome?
- SSRIs and MAOIs (Correct answer)
- Amoxicillin and ibuprofen
- Metformin and lisinopril
- Atorvastatin and amlodipine
Correct answer: SSRIs and MAOIs
Combining SSRIs with MAOIs inhibits serotonin breakdown while increasing its release, leading to potentially fatal serotonin syndrome.
Question 2: Warfarin's anticoagulant effect is significantly enhanced when co-administered with which of the following?
- Rifampicin
- Fluconazole (Correct answer)
- Cholestyramine
- Carbamazepine
Correct answer: Fluconazole
Fluconazole inhibits CYP2C9, the primary enzyme responsible for warfarin metabolism, thereby increasing warfarin plasma levels and bleeding risk.
Question 3: Methotrexate toxicity is significantly increased when given concurrently with which drug class?
- Beta-blockers
- Proton pump inhibitors
- NSAIDs (Correct answer)
- Antihistamines
Correct answer: NSAIDs
NSAIDs reduce renal clearance of methotrexate by inhibiting prostaglandin-dependent tubular secretion, leading to toxic accumulation.
Question 4: Which drug is absolutely contraindicated with sildenafil due to risk of severe hypotension?
- Atenolol
- Organic nitrates (Correct answer)
- Digoxin
- Furosemide
Correct answer: Organic nitrates
Both sildenafil and organic nitrates increase cGMP levels, causing profound additive vasodilation and potentially fatal hypotension.
Question 5: In the APC competency framework, identifying drug-drug interactions requires the pharmacist to review which primary resource first?
- Patient prescription history and current medication list (Correct answer)
- The patient's dietary habits
- Insurance formulary listings
- The prescriber's clinical notes only
Correct answer: Patient prescription history and current medication list
A complete current medication list is the essential starting point for identifying potential drug-drug interactions before dispensing.
Question 6: Quinolone antibiotics such as ciprofloxacin should not be administered simultaneously with antacids containing aluminum or magnesium because:
- They increase quinolone toxicity
- They cause chelation reducing quinolone absorption (Correct answer)
- They speed up quinolone metabolism
- They cause nephrotoxicity
Correct answer: They cause chelation reducing quinolone absorption
Divalent and trivalent cations in antacids chelate quinolones in the GI tract, forming insoluble complexes that drastically reduce oral bioavailability.
APC APC Drug Interactions and Contraindications 1
Which combination is a well-known clinically significant drug interaction that can increase the risk of serotonin syndrome?