The most appropriate treatment is pancreatic enzymes. This patient has steatorrhea and evidence of malnutrition (temporal wasting, poor dentition, hypoalbuminemia, and weight loss) that is attributable to exocrine pancreatic insufficiency from chronic pancreatitis. This diagnosis is based on established risk factors (past heavy and sustained alcohol use and cigarette smoking), clinical features (previous attacks of pancreatitis, current weight loss), and objective findings (pancreatic calcifications and steatorrhea). Exocrine insufficiency is treated using enteric-coated pancreatic enzymes. Steatorrhea that persists despite enzyme replacement may be treated by increasing the dose to 90,000 units of lipase per meal; confirming the diagnosis of pancreatic insufficiency by performing direct pancreatic function testing (if available); and excluding nonpancreatic causes, including bacterial overgrowth, celiac disease, and terminal ileal disease. Fat-soluble vitamin replacement is also important. Endocrine insufficiency can be difficult to manage because patients with chronic pancreatitis often lose counterregulatory hormones such as glucagon when their islet cells are destroyed, rendering their plasma glucose levels more labile. If diabetes mellitus occurs, it should be treated with insulin.

Loperamide and fiber are symptomatic therapies for chronic diarrhea. These are not appropriate in this patient because they do not treat the cause of steatorrhea or the associated weight loss and malnutrition.

A gluten-free diet is not appropriate because this patient's serologic testing for celiac disease was negative. Celiac disease is an established risk factor for acute and chronic pancreatitis and a cause of steatorrhea.