An overdose patient is barely breathing with pinpoint pupils; naloxone is given. Opioid overdose's triad — respiratory depression, pinpoint pupils, unconsciousness — reverses within minutes of naloxone (mu antagonist displacing the opioid). But naloxone's half-life is shorter than most opioids' — the patient can slip back; observe for hours, repeat doses. Fentanyl's potency makes street overdoses need multiple doses. Naloxone buys time — monitoring keeps it.