This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CHF, Angina Pectoris and Myocardial Infarction, Subject name: Pharmacology
The drug effective for treatment as well as prophylaxis of angina pectoris is: 
Select and explain. 
A. Isosorbide dinitrate, B. Pentaerythritol tetranitrate, C. Diltiazem, D. Dipyridamole
A: Isosorbide dinitrate
Answer: A: Isosorbide dinitrate 
Explanation: Isosorbide dinitrate Can be used sublingually at the time of attack (peak in 5-8 min) Orally for chronic prophylaxis. t 1/2 is 40 min, but sustained release formulation may afford protection for 6-10 hours. Nitrates are effective in classical as well as variant angina. Nitrates increase exercise tolerance and postpone ECG changes of ischemia.