1. Clinical Overview
Naloxone is a potent, competitive opioid receptor antagonist. It is the standard antidote for the complete or partial reversal of opioid-induced respiratory depression, including natural and synthetic opioids. In the 400mcg strength, it is primarily formulated for intranasal administration, providing a critical, rapid-response tool in community and pre-hospital settings for opioid overdose emergencies. It has no agonist activity and does not produce respiratory depression, psychotomimetic effects, or pupillary constriction.
| Onset | Duration | Bioavailability |
|---|---|---|
| Intranasal: 2-5 minutes; Intravenous: 1-2 minutes; Intramuscular: 2-5 minutes. | 30 to 90 minutes, depending on route and dose. Duration is shorter than that of many opioids, necessitating monitoring for re-narcotization. | Intranasal: Approximately 50% (varies with formulation and device). Intramuscular/Subcutaneous: ~40-50%. Intravenous: 100%. |
2. Mechanism of Action
Naloxone is a pure competitive antagonist at mu (μ), kappa (κ), and delta (δ) opioid receptors. It has the highest affinity for the μ-opioid receptor. It rapidly displaces opioid agonists from these receptors without activating them, thereby reversing all pharmacological effects of opioids, most critically the depression of the brainstem respiratory centers.
3. Indications & Uses
- Complete or partial reversal of opioid depression, including respiratory depression, induced by natural and synthetic opioids.
- Emergency treatment of known or suspected opioid overdose in community and healthcare settings.
- Diagnosis of suspected acute opioid overdosage.
4. Dosage & Administration
Adult Dosage: Opioid Overdose (Community/Intranasal): Administer 400 mcg (0.4 mg) intranasally as a single spray into one nostril. If no response after 2-3 minutes, administer a second dose using a new device. Repeat as necessary. Healthcare Setting (IV/IM/SC): Initial dose 400 mcg to 2 mg, repeat every 2-3 minutes as needed. If no response after 10 mg total, reconsider diagnosis.
Administration: Intranasal: Ensure patient is lying on their back. Peel back tab, insert nozzle into nostril, press plunger firmly. Do not prime or test. Administer into one nostril. For IV: Administer undiluted or diluted in NS. Give IV push slowly (over 30-60 seconds). Have resuscitation equipment available. Monitor patient continuously for re-narcotization for at least 2-4 hours post-administration.
5. Side Effects
Common side effects may include:
- Precipitation of Acute Opioid Withdrawal: Agitation, restlessness, nausea, vomiting, diarrhea, lacrimation, rhinorrhea, yawning, sweating, piloerection, abdominal cramps.
- Tachycardia, hypertension.
- Tremors, hyperventilation.
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Opioid Agonist-Antagonists (e.g., Pentazocine, Butorphanol, Nalbuphine) | May reduce analgesic effect and/or precipitate withdrawal symptoms. | Major |
| Opioid Partial Agonists (e.g., Buprenorphine) | High doses of naloxone may partially reverse effects, but buprenorphine's high receptor affinity may make reversal difficult and require higher/ repeated naloxone doses. | Major |
| Clonidine | Naloxone may reverse the hypotensive effects of clonidine. | Moderate |
| Cardiotoxic Drugs (e.g., Cocaine, Amphetamines) | Increased risk of severe hypertension, arrhythmias, and pulmonary edema upon abrupt opioid reversal. | Major |
7. Patient Counselling
- DO administer naloxone immediately if opioid overdose is suspected (signs: unresponsive, slow/no breathing, pinpoint pupils).
- DO call for emergency medical help (108/ambulance) immediately after or while administering the first dose.
- DO place the person in the recovery position after administration and monitor breathing until help arrives.
- DO NOT assume one dose is enough. Be prepared to give a second dose after 2-3 minutes if there is no response.
- DO NOT leave the person alone, as they may relapse into overdose (re-narcotization).
8. Toxicology & Storage
Overdose: Naloxone itself in excessive doses in non-opioid exposed individuals is relatively safe. In opioid-dependent patients, it causes severe withdrawal. In very high doses, theoretical risks include hypertension, tachycardia, and arrhythmias due to catecholamine release.
Storage: Store below 30°C. Protect from light. Do not freeze. Keep in the original container/carton until use. For prefilled intranasal devices, store in the provided case. Do not expose to direct sunlight. Keep out of reach of children. Check expiry date periodically.