A 52-year-old male with a 20-year history of heavy alcohol consumption presents with jaundice, ascites, and hepatic encephalopathy. Laboratory investigations show INR 2.8, serum bilirubin 4.2 mg/dL, and albumin 2.1 g/dL. He is diagnosed with decompensated alcoholic cirrhosis. Which drug is the first-line treatment to improve his survival and reduce portal hypertension complications?