Mr Brick is a well-known patient of yours, you saw him a few weeks ago following an episode of what seemed like cardiac chest pain and referred him to the rapid access chest pain clinic. He was investigated extensively and advised that his symptoms were caused by Angina and started on a variety of medications. He has come to see you today as he has had another two episodes of chest pain (like the one he had originally) where the pain quickly resolved. Mr Brick has a cardiology appointment in three months but is wondering if there is any other medication he can take to prevent the chest pain from happening. His current medication includes Aspirin, Ramipril, Atorvastatin, Metformin, Bisoprolol & Glyceryl Trinitrate spray.
Which one of the following medications would be the most suitable add-on therapy?