This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
Which of the following is NOT an alpha-adrenoceptor agonist? 
Select and explain. 
A. Clonidine, B. Methyldopa, C. Guanabenz, D. Isoxsuprine
D: Isoxsuprine
Answer: D: Isoxsuprine 
Explanation: Clonidine, apraclonidine, brimonidine are selective alpha 2 agonists. Guanfacine and guanabenz are central alpha 2 agonists. Isoxsuprine is a selective beta-2- receptor agonist used to relax uterus. From medical pharmacology Padmaja 4th edition page no 101