A 42-year-old man is found to be non-responsive in the emergency department with a respiratory rate of 6 breaths/min. After administration of naloxone, he improves significantly. What opioid is he most likely to have taken?

The most likely opioid the patient took is methadone taken orally. When considering the scenario of a 42-year-old man presenting with severe respiratory depression coupled with non-responsiveness, it's important to note the characteristics and effects of various opioids.

Methadone has a long half-life due to its extensive metabolism and is known for its potential to cause prolonged sedation and respiratory depression. This can lead to significant toxicity, especially in cases of overdose. The fact that naloxone administration resulted in a significant improvement in the patient's condition also suggests a potency associated with methadone, which can cause prolonged effects that persist even after naloxone is administered.

Other options, like fentanyl and hydromorphone, while potent, have shorter durations of action when given intravenously—making it less likely that a single dose would lead to such prolonged respiratory depression without resolution after naloxone. Similarly, oral morphine, although it can lead to respiratory depression, typically does not have the same long-lasting effects as methadone when taken in similar doses.

In summary, given the circumstances of severe respiratory distress, the long half-life, and the nature of the improvement with naloxone, methadone stands out as the most logical choice among the