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Amiodarone drug interactions — GPhC CRA MCQ

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HardDrug InteractionsAmiodarone drug interactionsGPhC CRA

A 74-year-old man with persistent atrial fibrillation is taking digoxin 125 micrograms once daily, warfarin, and amlodipine 5 mg once daily. His GP has added amiodarone 200 mg three times daily for one week, then 200 mg twice daily for one week, then 200 mg once daily as maintenance. What is the most important counselling point about the amiodarone?

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Correct answer: A — He may need dose reductions of digoxin and warfarin as amiodarone increases their levels

Amiodarone inhibits CYP3A4, CYP2C9, and P-glycoprotein, leading to increased plasma concentrations of both digoxin and warfarin. The BNF recommends halving the dose of digoxin and closely monitoring INR when amiodarone is initiated. Thyroid and liver function monitoring are also important, and patients should use high-factor sunscreen (SPF 50+), but the most important immediate counselling point relates to the drug interactions requiring dose adjustments.

Reference: https://www.pharmacyregulation.org/students-and-trainees/pharmacist-education-and-training/registration-assessment