A 64-year-old man presents with melena and postural dizziness. He is on low-dose ASA for secondary prevention. Blood pressure is 92/60 mm Hg and heart rate 112 beats/min. Hb is 85 g/L. After initial resuscitation with IV fluids and blood as required, which pharmacologic therapy should be started before endoscopy according to Canadian guidance for non-variceal upper gastrointestinal bleeding?