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: Pharmacology
Opioid available as nasal spray formulation is ? 
Select and explain. 
A. Tramadol, B. Codiene, C. Butorphanol, D. Buprenorphine
C: Butorphanol
Answer: C: Butorphanol 
Explanation: Ans. is'c'i.e., Butorphanol [Ref: KDT 7h/e p. 482)Butorphanol - Nasal spray (Stadol)