Amiodarone × Atorvastatin

Amiodarone moderately blocks CYP3A4 – a partial atorvastatin metabolic route. Atorvastatin plasma levels rise 1.5- to 2-fold; myopathy risk grows at doses of 40 mg and above.

Pain and weakness in large muscle groups (thighs, shoulders, calves), dark urine, elevated creatine kinase. Severe cases progress to rhabdomyolysis with acute kidney injury. Symptoms appear within 1–4 weeks of co-administration.

Cap atorvastatin at 20 mg/day when amiodarone is added. If LDL targets are missed, switch to pravastatin or rosuvastatin (less CYP3A4-dependent). Check creatine kinase at 4–6 weeks and on muscle symptoms.