====== Naloxone (Narcan®) ======

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<WRAP infobox>
^ Naloxone | {{ :neuro:opioids:naloxone.svg?200 |}} |
| Brand Names | Narcan®, Kloxxado® |
| Drug Class | [[neuro:opioids:start|Opioid Antagonist]] |
| Primary Indication | Opioid Overdose |
| Mechanism | Competitive μ receptor antagonist |
| Onset | 1–2 minutes (IV) |
| Duration | 30–90 minutes |
| Controlled Substance | No |
| FDA Approval | 1971 |
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</WRAP>

===== Overview =====

Naloxone is a competitive opioid receptor antagonist used for the reversal of opioid-induced respiratory depression.

It has highest affinity for the μ-opioid receptor and rapidly displaces opioid agonists such as morphine, oxycodone, fentanyl, and heroin.

Naloxone reverses respiratory depression but may precipitate acute withdrawal in opioid-dependent patients.

<WRAP clear></WRAP>

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===== Mechanism of Action =====

**Receptor Activity**
  * Competitive antagonist at μ-opioid receptors  
  * Also antagonizes κ and δ receptors  

**Pharmacologic Effect**
  * Displaces opioid agonists from receptors  
  * Reverses respiratory depression  
  * Reverses CNS depression  

No intrinsic agonist activity.

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===== Indications =====

  * Suspected opioid overdose  
  * Respiratory depression from opioid use  
  * Iatrogenic opioid-induced respiratory depression  

Used in:
  * Emergency departments  
  * Prehospital settings  
  * Community overdose response  

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<WRAP details>
===== Dosing =====

IV (hospital setting):
  * 0.04–0.4 mg initially  
  * Titrate to adequate respiratory effort  

Intranasal (community use):
  * 4 mg per spray  
  * Repeat every 2–3 minutes if needed  

Goal:
  * Restore spontaneous breathing  
  * NOT full arousal  

May require repeat dosing due to short half-life.

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<WRAP details>
===== Pharmacokinetics =====

Onset:
  * IV: 1–2 minutes  
  * Intranasal: 2–3 minutes  

Half-life:
  * ~30–90 minutes  

Duration:
  * Often shorter than long-acting opioids  

Metabolism:
  * Hepatic  

Elimination:
  * Renal  

Re-sedation can occur after naloxone wears off.

</WRAP>

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<WRAP details>
===== Adverse Effects =====

  * Acute opioid withdrawal  
  * Agitation  
  * Tachycardia  
  * Hypertension  
  * Nausea / vomiting  
  * Pulmonary edema (rare)  

In opioid-dependent patients, rapid reversal may cause severe withdrawal symptoms.

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<WRAP pearls>
===== Clinical Pearls =====

  * Naloxone reverses respiratory depression, not necessarily pain.  
  * Duration is shorter than many opioids → monitor for re-sedation.  
  * May require repeated dosing for long-acting opioids (e.g., methadone).  
  * Use lowest effective dose to restore respirations.  
  * Widely available over-the-counter in many states.  

</WRAP>

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===== Toxicology Considerations =====

Classic opioid toxidrome:
  * CNS depression  
  * Respiratory depression  
  * Miosis  

Naloxone confirms diagnosis if rapid improvement occurs.

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===== Comparison Within Class =====

Compared to [[neuro:opioids:naltrexone|Naltrexone]]:
  * Short-acting  
  * Used for acute reversal  

Compared to [[neuro:opioids:methylnaltrexone|Methylnaltrexone]]:
  * Crosses blood-brain barrier  
  * Reverses central effects  

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===== Related =====

  * [[neuro:opioids:start|Opioids]]
  * [[neuro:opioids:morphine|Morphine]]
  * [[neuro:opioids:fentanyl|Fentanyl]]
  * [[neuro:opioids:hydromorphone|Hydromorphone]]
  * [[neuro:opioids:naltrexone|Naltrexone]]