This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
Which of the following is a skeletal muscle relaxant that acts as a central a2 adrenergic agonist: 
Select and explain. 
A. Tizanidine, B. Brimonidine, C. Chlormezanone, D. Quinine
A: Tizanidine
Answer: A: Tizanidine 
Explanation: * Tizanidine and brimonidine are alpha2 adrenergic agonists. Tizanidine is used as a centrally acting muscle relaxant whereas brimonidine is used topically for the treatment of glaucoma. * Chlormezanone is a centrally acting muscle relaxant that acts by inhibiting the spinal internuncial neurons. * Quinine is a directly acting peripheral muscle relaxant.