Which medication is used to treat the client with a heroin overdose? A. Methodone (Dolophine) B. Flumazenil (Romazicon) C. Naloxone (Narcan) D. Physostigmine (Antilirium)

First, the student needs to understand the concept of a heroin overdose and the consequences it has on the body. Heroin is an opioid drug, and an overdose can lead to severe respiratory depression, coma, and potentially death.

The student should familiarize themselves with the medications provided in the options. Each medication has a specific purpose and mechanism of action, which makes it suitable for certain conditions. A. Methadone (Dolophine) is used to treat opioid addiction as part of a maintenance program, but it's not used for treating an opioid overdose. B. Flumazenil (Romazicon) is used as an antagonist for benzodiazepines, mainly in cases of benzodiazepine overdose; it has no direct effect on opioids. C. Naloxone (Narcan) is an opioid antagonist, designed to reverse the effects of opioids, including respiratory depression and sedation. It is commonly used in emergency situations to quickly reverse an opioid overdose. D. Physostigmine (Antilirium) is used for the treatment of anticholinergic poisoning. It's not a treatment for opioid overdose.

Among the presented options, C. Naloxone (Narcan) is the medication specifically designed to reverse an opioid overdose's effects, making it the appropriate choice for treating a heroin overdose. Hence, the correct answer is: C. Naloxone (Narcan)