A patient with chronic-stable angina is on prophylactic beta-blocker therapy, with sublingual nitroglycerin used PRN (as needed) for managing acute angina. One day he experiences particularly severe angina that is not relieved by sublingual nitroglycerin. What is the most appropriate next step in management?
1) Increase the dose of beta-blocker
2) Administer intravenous nitroglycerin
3) Administer aspirin
4) Administer a calcium channel blocker