Lipid Biochemistry USMLE Step 1 Practice Question
A 52-year-old woman on atorvastatin and ezetimibe for hypercholesterolemia presents with diffuse myalgias and dark urine. Vital signs: BP 128/82, HR 88, RR 16, Temp 37.2°C, SpO2 98%. LDL cholesterol decreased from 150 to 45 mg/dL as intended. Serum creatine kinase is elevated at 1,200 U/L. Urinalysis shows myoglobin. She denies recent trauma or strenuous exercise. Which mechanism best explains this adverse drug interaction?
Answer choices
- AEnhanced activation of muscle lipoprotein lipase causing cellular lipid overload
- BIncreased statin bioavailability due to inhibition of hepatic metabolism by ezetimibeCorrect answer
- CCompetitive inhibition of LDL receptor binding by ezetimibe
- DEzetimibe directly inhibits muscle mitochondrial HMG-CoA reductase
- EImpaired CoQ10 synthesis in muscle due to combined statin-ezetimibe effect
- FInduction of hepatic cytochrome P450 enzymes leading to increased statin metabolism and compensatory dosing
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