This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2017, Subject name: Pharmacology
A female in labor ward was administered opioid analgesic. Which of the following drugs should be kept ready for emergency? 
Select and explain. 
A. Lignocaine, B. Naloxone, C. Diphenhydramine, D. Fentanyl
B: Naloxone
Answer: B: Naloxone 
Explanation: Naloxone is an opioid anatagonist given intravenously. It blocks mu, kappa and delta receptors. It is the DOC for opioid toxicity. Lignocaine is a local anaesthetic. Diphenhydramine is a first generation antihistaminic. Fentanyl is a synthetic opioid.