A 32-year-old woman is brought to the emergency department because of fever, hallucinations, agitation, and confusion for 8 hours. She has a history of alcohol, cocaine, and benzodiazepine abuse. Her temperature is 37.8°C (100°F), pulse is 110/min, respirations are 16/min, and blood pressure is 150/90 mm Hg. Examination shows tremors and telangiectasia. The lungs are clear to auscultation. There is a holosystolic murmur; the abdomen is tender, and the liver edge is palpable 3 cm below the right costal margin. Rectal examination shows no abnormalities. Her serum alkaline phosphatase activity is 200 U/L, serum ALT activity is 60 U/L, and serum AST activity is 90 U/L. Which of the following is the most likely cause of this condition?