Roger Jenkinson is a 73 year old gentleman who presents with dysphagia and weight loss which has been affecting him for the past 8 weeks. He denies any abdominal pain or change in bowel habit. He suffers with Hypertension and was a heavy smoker in the past. He does not drink alcohol. He is currently prescribed Amlodipine, Atorvastatin, Losartan and Omeprazole. After discussion, an urgent upper gastrointestinal endoscopy referral is arranged to investigate a suspected upper gastrointestinal cancer. When should he stop taking his Omeprazole?