This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
A patient in labor ward was given opioid analgesic. Which drug should be kept ready for emergency? 
Select and explain. 
A. Naloxone, B. Lignocaine, C. Diphenhydramine, D. Fentanyl
A: Naloxone
Answer: A: Naloxone 
Explanation: ANS. A# Opioid antagonists1. Naloxone2. Natrexone3. Nalmefene# Clinical uses of Naloxone1. Drug of choice for morphine poisoning (0.4-0.8 mg IV every 2-3 min; max 10 mg)2. To reverse the respiratory depression due to intraoperative use of opioids3. Diagnosis of opioid dependence4. Partially reverses alcohol intoxication