Drug–Drug, Drug–Food, Drug–Disease Practice Test

A 63-year-old female (70 kg, 162 cm) is starting levothyroxine 75 mcg PO daily for newly diagnosed hypothyroidism. She reports she takes her medications each morning with coffee and a high-fiber cereal, and she also takes calcium carbonate 500 mg elemental calcium PO twice daily and ferrous sulfate 325 mg PO daily. Medical history: osteoporosis and iron-deficiency anemia. Labs: TSH 12.8 mIU/L (ref 0.4–4.0), free T4 0.6 ng/dL (ref 0.8–1.8), SCr 0.9 mg/dL (ref 0.6–1.3). Allergies: none. What dietary advice should be provided to avoid interactions?

A 60-year-old female (74 kg, 165 cm) is picking up a new prescription for clarithromycin 500 mg PO twice daily for 10 days for community-acquired pneumonia. Medical history: hyperlipidemia, type 2 diabetes, and GERD. Current medications: simvastatin 40 mg PO nightly, metformin 1000 mg PO twice daily, omeprazole 20 mg PO daily, and aspirin 81 mg PO daily. Labs: AST/ALT 28/31 U/L (ref 10–40), SCr 0.9 mg/dL (ref 0.6–1.3), A1c 7.4% (ref 4.0–5.6). Allergies: none. Which drug interaction poses the greatest risk to this patient?