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Naloxone (Narcan, Kloxxado)

Opioid receptor antagonist (antidote)

Mechanism of action

Pure mu-opioid receptor antagonist with high affinity — displaces opioids from the receptor, reversing respiratory depression and sedation within minutes. Has no agonist activity, so it cannot cause respiratory depression itself. Half-life is shorter than most opioids — re-narcotization (return of opioid effect) is the central monitoring concern.

Adverse effects

Life-threatening / NCLEX-tested

  • Acute opioid withdrawal — severe agitation, hypertension, tachycardia, vomiting, sweating, piloerection in opioid-dependent patients (especially babies of opioid-using mothers)
  • Pulmonary edema (uncommon, more often reported in surgical reversal scenarios)
  • Severe hypertension and tachyarrhythmia, with rare reports of MI in patients with cardiac disease
  • Seizures (rare, in mixed overdoses)
  • Re-narcotization once naloxone wears off — recurrence of respiratory depression

Side effects

Common — what to teach

  • Nausea, vomiting
  • Sweating
  • Trembling
  • Headache
  • Anxiety, agitation
  • Mild flushing

Food & drug interactions

Generally minimal. Reverses ALL opioids — including buprenorphine (partial agonist; naloxone may displace it but high doses may be needed) and methadone (very long half-life — patient needs prolonged monitoring after reversal). Reverses opioid-induced histamine effects and ileus.

Nursing implications

Assessment, monitoring, patient teaching

  • Indication: respiratory depression (RR < 12) and/or unresponsiveness with suspected opioid involvement
  • Routes/doses: IM 0.4 mg, intranasal 4 mg or 8 mg sprays, IV 0.04–0.4 mg titrated; repeat every 2–3 minutes as needed
  • Titrate to respiratory rate (≥ 12) and adequate ventilation, NOT to full alertness — overshooting causes severe withdrawal in dependent patients
  • MONITOR for re-narcotization for at least 2 hours after the last dose (longer for long-acting opioids like methadone, sustained-release oxycodone, fentanyl patches) — naloxone can wear off before the opioid does
  • Always continue rescue breathing/ventilation while naloxone takes effect
  • Take-home naloxone: counsel families on every opioid prescription; teach the steps — call 911, give naloxone, rescue breaths, recovery position
  • Newborns of opioid-using mothers: AVOID naloxone — precipitates severe neonatal withdrawal; treat respiratory depression with ventilation

When to hold / contraindications

  • Newborns of opioid-using mothers (use ventilation instead)
  • Suspected non-opioid cause of respiratory depression — may waste time
  • Hypersensitivity to naloxone (rare)
  • Note: there is no clinical reason to "hold" naloxone in active opioid overdose — give it; the question is dose and route

Memory anchor

"Narcan reverses, then wears off." Watch at least 2 hours; longer for methadone or fentanyl patches. Titrate to RR ≥ 12, not to full alertness — overshoot causes withdrawal.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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