CDN Pharmacology & Drug-Nutrient Interactions 1 — Questions and Answers
Question 1: Which antibiotic class chelates divalent cations such as calcium, magnesium, and zinc, significantly reducing their absorption when taken together?
- Penicillins
- Tetracyclines (Correct answer)
- Macrolides
- Cephalosporins
Correct answer: Tetracyclines
Tetracyclines form insoluble complexes with divalent and trivalent cations, impairing both antibiotic and mineral absorption.
Question 2: Patients on warfarin (Coumadin) anticoagulation therapy require careful monitoring of their intake of which vitamin?
- Vitamin A
- Vitamin C
- Vitamin K (Correct answer)
- Vitamin E
Correct answer: Vitamin K
Vitamin K is essential for the synthesis of clotting factors II, VII, IX, and X; fluctuating intake directly affects warfarin's anticoagulant effect.
Question 3: Long-term use of proton pump inhibitors (PPIs) most commonly leads to clinically significant deficiency of which nutrient?
- Iron
- Vitamin D
- Vitamin B12 (Correct answer)
- Zinc
Correct answer: Vitamin B12
PPIs suppress gastric acid, which is required to cleave vitamin B12 from dietary protein and for intrinsic factor–mediated absorption.
Question 4: Metformin, a first-line medication for type 2 diabetes, is associated with reduced absorption of which vitamin over time?
- Vitamin A
- Vitamin B12 (Correct answer)
- Vitamin D
- Folate
Correct answer: Vitamin B12
Metformin interferes with calcium-dependent absorption of the vitamin B12–intrinsic factor complex in the terminal ileum.
Question 5: Which beverage most significantly interacts with statin medications by inhibiting CYP3A4 and increasing the risk of myopathy?
- Orange juice
- Grapefruit juice (Correct answer)
- Apple juice
- Cranberry juice
Correct answer: Grapefruit juice
Grapefruit juice contains furanocoumarins that irreversibly inhibit intestinal CYP3A4, dramatically increasing statin plasma levels and toxicity risk.
Question 6: Patients prescribed monoamine oxidase inhibitors (MAOIs) must restrict dietary intake of which substance to prevent a potentially fatal hypertensive crisis?
- Histamine
- Tyramine (Correct answer)
- Tryptophan
- Phenylalanine
Correct answer: Tyramine
MAOIs prevent the breakdown of tyramine in the gut and liver; tyramine accumulation triggers massive catecholamine release, causing severe hypertension.
Question 7: Isoniazid (INH), used in the treatment of tuberculosis, acts as a structural antagonist to which B vitamin, frequently necessitating supplementation?
- Thiamine (B1)
- Riboflavin (B2)
- Pyridoxine (B6) (Correct answer)
- Cobalamin (B12)
Correct answer: Pyridoxine (B6)
Isoniazid structurally resembles pyridoxine and competitively inhibits its conversion to the active coenzyme pyridoxal-5-phosphate, causing peripheral neuropathy.
CDN Pharmacology & Drug-Nutrient Interactions 1
Which antibiotic class chelates divalent cations such as calcium, magnesium, and zinc, significantly reducing their absorption when taken together?