A client who is obtunded arrives in the emergency department with a suspected drug overdose. The client becomes responsive after the administration of IV naloxone, but within a short period, the client's level of consciousness decreases again and the respiratory rate decreases to 6 breaths/minute. Which action should the nurse take first?

A. Administer an additional dose of naloxone: Naloxone has a shorter half-life than many opioids, so symptoms of overdose, including respiratory depression, can return after its effects wear off. Administering an additional dose promptly reverses opioid toxicity and improves breathing. B. Prepare to initiate cardiopulmonary resuscitation (CPR): Although respiratory depression is critical, CPR is not immediately indicated unless the client is unresponsive with absent pulse or cardiac arrest. The priority is to restore adequate breathing first. C. Determine if results of the drug toxicity screen are available: While helpful for diagnosis, waiting for lab results delays urgent treatment needed to address life-threatening respiratory depression. Immediate intervention takes precedence. D. Initiate a second intravenous access site: Establishing additional IV access may be useful but is not the first priority in an emergency situation where respiratory failure requires immediate reversal with naloxone.