GF is a 58 year old male who presents to his primary care manager for his annual checkup. His past medical history is significant for hypertension, allergic rhinitis, and GERD. He currently takes diltiazem 240mg daily, hctz 25mg daily, loratadine 10mg daily, and omeprazole 20mg daily. Based on GF's lipid profile and current CV risk, the decision is made to start statin therapy, specifically simvastatin. Which of the following is true regarding dosing of simvastatin with GF's current medication regimen?
A. The dose of simvastatin should not exceed 40mg daily.
B. The dose of simvastatin should not exceed 20mg daily.
C. The dose of simvastatin should not exceed 10mg daily.
D. The dose of simvastatin should not exceed 5mg daily.
Answer with rationale:
The correct answer is C. Close attention is required when administering simvastatin with certain medications due to the potential for decreased simvastatin metabolism and increased risk of toxicity due to CYP 3A4 inhibition. Additionally, grapefruit juice due to its potent CYP 3A4 inhibition should be avoided with simvastatin therapy. There are some medications such as itraconazole or clarithromycin (common with H. pylori regimens) that are contraindicated with simvastatin. Answer C is correct as this patient is receiving dilitiazem which necessitates a dose maximum of 10mg daily. The other medications on GF's profile do not require adjustment of simvastatin making the other answers incorrect.
For further information on these potential interactions see the following simvastatin package insert: