Which of the following medications should the nurse plan to administer to a client who has heroin toxicity, is unresponsive, has pinpoint pupils, and a respiratory rate of 8/min?

The correct answer is B: Naloxone. Naloxone is an opioid antagonist that reverses the effects of opioids like heroin. In this scenario, the client's symptoms of unresponsiveness, pinpoint pupils, and respiratory depression indicate opioid toxicity. Naloxone will competitively bind to opioid receptors, reversing respiratory depression and potentially restoring consciousness. Methadone (A) is used for opioid dependence but not acute toxicity. Diazepam (C) is a benzodiazepine and not indicated for opioid toxicity. Bupropion (D) is an antidepressant and not appropriate for this situation.