A youth is brought into the emergency department by paramedics after being found unconscious lying on a sewer grate. No further history is available. In the triage unit, the patient’s respiratory rate is 8 breaths per minute, and breaths are shallow. Heart rate is 50 beats per minute. Oxygen saturation by pulse oximetry is 90% on room air. Pupils are constricted and fixed. “Track marks” are noted on the forearms. The triage nurse applies oxygen by mask and the emergency resident orders a medication given through an intravenous line. Three minutes later the patient is awake, agitated, and complaining of severe generalized pain. Respiratory rate is 30 breaths per minute. When the medicine resident arrives at the bedside an hour later to admit the patient, the youth is once more unconscious, breathing slowly and shallowly as on arrival in triage.