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
All are true about nitrous oxide except ? 
Select and explain. 
A. Laughing gas, B. Causes megaloblastic anemia, C. Causes diffusion hypoxia, D. Good muscle relaxant
D: Good muscle relaxant
Answer: D: Good muscle relaxant 
Explanation: Ans. is 'd' i.e., Good muscle relaxant Nitrous oxide N,O It is also called laughing gas. It has good analgesic but poor muscle relaxant activity. Second gas effect and diffusion hypoxia occur with N20 only. N20 is the only anaesthetic repoed to produce hematologic toxicity and neurotoxicity with long term administration. Both toxicities are the result of the interaction of N20 with vit B12.