Naloxone hydrochloride
Brand names: Prenoxad, Nyxoid (intranasal), Narcan
The hydrochloride salt of naloxone, a competitive opioid receptor antagonist, used as the emergency treatment of known or suspected opioid overdose and opioid-induced respiratory depression.
ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.
Clinical monograph
How it works
Naloxone hydrochloride competitively displaces opioid agonists from mu opioid receptors, rapidly reversing opioid-induced respiratory depression, sedation and analgesia.
Prescribing in practice
- Because its action may wear off before the opioid does, repeated dosing or an infusion with continued monitoring is needed to prevent recurrence of respiratory depression.
- Reversal in opioid-dependent individuals can trigger acute withdrawal, so titrate carefully to adequate respiration.
- It has no effect on respiratory depression of non-opioid origin and should be combined with supportive airway and ventilatory care.
Monitoring
Closely monitor respiratory rate, oxygenation and level of consciousness for an extended period, repeating doses as the opioid effect re-emerges.
Counselling the patient
- Continued observation is essential after treatment because the overdose can recur as the antidote fades.
- Carers should still summon emergency help even if the person initially wakes after naloxone.
Evidence & guidelines
Naloxone hydrochloride is the established antidote for opioid overdose, recommended in resuscitation, toxicology and take-home naloxone guidance.
Reference: UK Resus Council; PHE/UK guidelines drug misuse; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.
- Morphine Milligram Equivalents (MME) Calculator · Pain / Opioids
- Opioid Conversion / Equianalgesic Guide · Pain Management
- Numeric Rating Scale (NRS) Pain Assessment and Management · Pain Management
- Finnegan Neonatal Abstinence Scoring Tool (FNAST) · Neonatal Abstinence Syndrome
- Myasthenia Gravis Activities of Daily Living (MG-ADL) Scale · Neuromuscular
- Modified Finnegan Neonatal Abstinence Score (NAS) · Neonatal
- Difficult Airway Algorithm (DAS) · DAS 2015; Royal College of Anaesthetists
- Major Haemorrhage Protocol · NICE NG24; UK MHP guidelines
- New-Onset Atrial Fibrillation · ESC 2020 AF Guidelines; NICE NG196
- Hypertensive Emergency · ESC/ESH 2018 Hypertension Guidelines; NICE NG136
- Bradycardia Management · Resuscitation Council UK ABCDE; ESC 2021 Pacing Guidelines
- Ventricular Tachycardia / Fibrillation · Resuscitation Council UK ACLS; ESC 2022 Ventricular Arrhythmia Guidelines
Featured in these MRCEM clinical pathways
Naloxone hydrochloride is a core drug in the following exam-focused workups on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.