American Board of Internal Medicine (ABIM) Certification Practice Exam

To decrease the risk for myopathy, the dose of simvastatin should be limited to what when taken with amiodarone?

1. 40 mg/d

2. 30 mg/d

3. 20 mg/d

4. 10 mg/d

The correct answer is: 20 mg/d

When simvastatin is taken in conjunction with amiodarone, the risk of myopathy, including rhabdomyolysis, increases. This interaction is primarily due to the effects that amiodarone has on the metabolism of simvastatin. Amiodarone inhibits the cytochrome P450 enzyme system, specifically CYP3A4, which plays a significant role in the metabolism of simvastatin. To mitigate this risk, the recommended maximum daily dose of simvastatin when used concurrently with amiodarone is 20 mg. This dose reduction is crucial because it helps maintain efficacy while reducing the likelihood of adverse effects like muscle damage. By choosing a limit of 20 mg daily, healthcare providers can ensure that patients receive the necessary lipid lowering effect from simvastatin while minimizing the potential harms associated with drug interactions. This precautionary approach is especially important in clinical settings where patients may be taking multiple medications.