This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
First dose hypotension is caused by : 
Select and explain. 
A. Prazosin, B. Clonidine, C. Sodium nitroprusside, D. Propranolol
A: Prazosin
Answer: A: Prazosin 
Explanation: Ans. is 'a' Prazosin Prazosin is a highly selective alpha1 blocker*It dilates arterioles more than veins*It is effective orally *It causes first dose hypotension *It is primarily used as an antihypertensiveIts initial dose should be low