Lipid Biochemistry USMLE Step 1 Practice Question
A 52-year-old man on atorvastatin 40 mg daily for hypercholesterolemia presents with acute myalgia and proximal muscle weakness. Vital signs: BP 138/82, HR 88, RR 16, Temp 37.2°C, SpO2 98% on room air. He started clarithromycin 500 mg twice daily 5 days ago for community-acquired pneumonia. Creatine kinase is markedly elevated at 8,500 U/L; urinalysis shows no myoglobinuria. Which mechanism explains the increased risk of statin-induced myopathy with this drug combination?
Answer choices
- AStatins deplete muscle ubiquinone independent of drug interactions
- BClarithromycin inhibits hepatic CYP3A4, increasing statin blood levelsCorrect answer
- CClarithromycin directly inhibits HMG-CoA reductase in muscle tissue
- DCombined therapy decreases CoA synthesis in mitochondria
- EStatins increase muscle protein degradation through autophagy
- FClarithromycin inhibits hepatic CYP2D6, preventing atorvastatin metabolism
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