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
[{'content': 'Which of the following drugs has been used in the treatment of angina by inhalation and has a very rapid onset and brief duration of action? \nSelect and explain. \nA. Amyl nitrite, B. Isosorbide mononitrate, C. Nitroglycerine, D. Propanolol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Amyl nitrite is given by inhalational route and used in cyanide poisoning. The inhalation route provides very rapid absorption and, like the sublingual route, avoids the hepatic first-pass effect. Because of its unpleasant odor and extremely sho duration of action, amyl nitrite is now obsolete for angina. Amyl nitrite is a highly volatile liquid. It is available in fragile glass ampules packaged in a protective cloth covering.Ampule has to be crushed with fingers, and the vapors have to be inhaled through protective covering. This antidote for cyanide poisoning is Hydroxocobalamin (IV) , a form of vitamin B12, which also has a very high affinity for cyanide and combines with it to generate another form of vitamin B12.', 'role': 'assistant'}]