This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Best LA agent for intranasal instillation: \nSelect and explain. \nA. Articaine, B. Tetracaine, C. Lignocaine, D. Bupivacaine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: It is formulated in a pre-filled, single-use nasal sprayer: 6 mg tetracaine HCl and 0.1 mg oxymetazoline HCl (equivalent to 5.27 mg tetracaine and 0.088 mg oxymetazoline) in each 0.2 mL spray. It is intended for intranasal use only, and administration should be on the same side as the maxillary tooth being treated. It is recommended to wait 10 minutes after administration and then determine anesthesia effectiveness.\nTopical tetracaine has been safely and effectively used intranasally by the ear-nose-throat (ENT) medical community for ENT procedures. Patients noticed that their upper teeth felt numb, which led to interest in the application of this type of anesthesia for dentistry. The oxymetazoline (the active ingredient in Afrin and other nasal decongestant sprays) was added to Kovanaze to slow systemic absorption of the tetracaine and improve the duration of action.\nhttps://www.rdhmag.com/patient-care/article/16409318/needleless-intranasal-spray-kovanaze-product-for-local-anesthesia-makes-its-debut', 'role': 'assistant'}]