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: Forensic Medicine
A 34 year old rickshaw puller has been using heroin for the past ten years. One evening his family members found him unconscious. He was brought to the casualty. On examination he had bradycardia, shallow breathing, constricted pupils. His blood pressure was 100/70 mm of Hg. He had brisk bilateral deep tendon reflexes. The plantar reflexes were flexor on both sides. Which of the following is the best treatment for him ? 
Select and explain. 
A. Buprenorphine, B. Flumazenil, C. Methadone, D. Naloxone
D: Naloxone
Answer: D: Naloxone 
Explanation: Bradycardia, shallow breathing, constricted pupil and hypotension, in a person with history of heroin abuse, suggest the diagnosis of heroin poisoning.
Drug of choice for opioid poisoning (intoxication) is IV naloxone.