# Naloxone HCl: veterinary dose and monograph

> Naloxone HCl is a veterinary drug. Pure mu-opioid antagonist — used for reversal of opioid-induced respiratory depression, dysphoria, sedation, and apnoea. Indications include reversal of opioid-induced respiratory depression; reversal of post-op opioid dysphoria; neonate / foal apnoea after maternal opioid analgesia (caesarean). This monograph lists 5 reference doses for dogs, cats, horses and rabbits, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/naloxone · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Narcan
- **Species with doses:** Dogs, Cats, Horses and Rabbits
- **General dose range:** 0.01–0.04 mg/kg IV titrate to effect (repeat q30 min) — check the species tables for the indication
- **Routes:** IV
- **Last reviewed:** 1 October 2026

## Indications

- Reversal of opioid-induced respiratory depression
- Reversal of post-op opioid dysphoria
- Neonate / foal apnoea after maternal opioid analgesia (caesarean)
- Buprenorphine overdose (higher doses needed due to tight receptor binding)
- Diagnostic — confirms opioid involvement in mystery sedation

## Naloxone HCl dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Naloxone HCl doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Opioid reversal — titrate to respiratory effort | 0.01–0.04 mg/kg | IV | repeat as needed | — |
| Dysphoria from full-mu opioid | 0.004 mg/kg | IV | titrate 1 mL/min of the dilution | — |

- Opioid reversal — titrate to respiratory effort: Papich 5e: 0.01–0.04 mg/kg IV, IM or SC as needed; a full antagonist dose is 0.04 mg/kg. Plumb’s p.873: 0.01–0.02 mg/kg IM, IV or SC (Trim 2008); 0.04 mg/kg (label). Naloxone is shorter-acting than most opioids — watch for re-narcotisation and redose.
- Dysphoria from full-mu opioid: Plumb’s p.873 (Dyson 2008): 4 µg/kg diluted to 10 mL and given in 1 mL increments every minute to effect. Papich 5e: 1 mL every 30 s of a 0.04 mg/mL dilution as needed. Stops the dysphoria while preserving some analgesia.

### Cats

*Naloxone HCl doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Opioid reversal | 0.01–0.04 mg/kg | IV | q30–60 min as needed | — |

- Opioid reversal: Papich 5e and Plumb’s p.873 give dogs and cats the same range: 0.01–0.04 mg/kg IV, IM or SC (full antagonist 0.04 mg/kg). Neonates after caesarean: one drop of 0.4 mg/mL under the tongue (Dyson 2008).

### Horses

*Naloxone HCl doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Opioid reversal (esp. butorphanol / morphine sedation) | 0.01–0.04 mg/kg | IV | q30–60 min as needed | — |

- Opioid reversal (esp. butorphanol / morphine sedation): Plumb’s p.873: 0.01–0.022 mg/kg to reverse sedative and excitatory effects of opioid agonists (Clark & Becht 1987); 0.01 mg/kg IV limits locomotor activity (Muir 1987). Papich 5e: 0.02–0.04 mg/kg IV — duration of effect only about 20 min. ARCI Class 3.

### Pigs

*Naloxone HCl doses for pigs*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| No reference dose for this species | Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species | — | — | — | — |

- No reference dose for this species: The previous 0.01–0.04 mg/kg row for pigs had no source; neither Papich 5e nor Plumb’s gives a pig naloxone dose.

### Rabbits

*Naloxone HCl doses for rabbits*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Opioid reversal in rabbits | 0.005–0.1 mg/kg | IV | q30–60 min as needed | — |

- Opioid reversal in rabbits: Plumb’s p.873 (Ivey & Morrisey 2000): rabbits 0.005–0.1 mg/kg IM or IV. Rodents 0.01–0.1 mg/kg SC or IP (Adamcak & Otten 2000).

## Contraindications

Known hypersensitivity. Caution: full reversal of analgesia in animals with severe pain is contraindicated — titrate to respiratory effort only. Withdrawal seizures in opioid-dependent patients (rare in veterinary practice).

## Species-specific warnings

> **Caution:** Dogs: Titrate to respiratory effort — full reversal causes pain crisis. Buprenorphine needs higher repeated doses.

> **Caution:** Rabbits: Rabbits metabolise opioids fast — repeat naloxone may be needed within 20–30 min.

## Adverse effects

- Acute pain crisis (rapid full reversal of analgesia)
- Tachycardia / hypertension
- Tremor / hyperalgesia
- Vomiting (sudden return of GI motility)

## Drug interactions

- Reverses ALL opioid effects — including analgesia (titrate carefully to respiratory effort only)
- No clinically significant non-opioid interactions

## Pregnancy and lactation

Safe — used in neonate / foal apnoea after maternal caesarean. FDA Category B (human).

## Monitoring

- Respiratory rate / SpO2 — primary endpoint
- Repeated assessment every 30–60 min — opioid often outlasts naloxone
- Pain score — if reversed analgesia, redose opioid at low dose
- Heart rate / blood pressure (acute reversal can cause tachycardia / hypertension)

## Toxicity and overdose

Management: No specific toxicity at clinical doses. Concern is from acute pain crisis if over-reversed — re-administer opioid at half-original dose for analgesia.

## Clinical pearls

- Post-op opioid dysphoria: 1–5 µg/kg IV partial reversal clears dysphoria while preserving analgesia — KEY pearl for surgery recovery
- Foal born from caesarean with maternal morphine on board: 0.02 mg/kg IV in umbilical vein → instant respiratory response
- Buprenorphine overdose needs HIGHER repeated naloxone doses (0.04 mg/kg IV q30 min × multiple doses) — buprenorphine tightly binds receptors
- Rabbit overdose: 0.05 mg/kg IV; rabbits metabolise fast so opioid AND naloxone clear quickly
- Always have naloxone drawn up and on the anaesthesia tray during any opioid-based surgery

## Mechanism of action

Pure competitive antagonist at mu (preferred), kappa, and delta opioid receptors. Displaces opioid agonists, reversing their effects within 1–2 min IV. Onset 1–2 min, peak 5 min, duration 30–60 min. No intrinsic agonist activity → no respiratory depression of its own at any dose. Repeated dosing or CRI (5–20 µg/kg/h) often needed for long-acting opioids (morphine, methadone) or buprenorphine.

## Formulations and products

- Naloxone 0.4 mg/mL injection
- Naloxone 1 mg/mL injection

## Storage

15–25 °C, protect from light.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Naloxone HCl for dogs?

Reference doses for Naloxone HCl in dogs: 0.01–0.04 mg/kg IV repeat as needed (Opioid reversal — titrate to respiratory effort); 0.004 mg/kg IV titrate 1 mL/min of the dilution (Dysphoria from full-mu opioid). Confirm against the label and the patient before use.

### What is the dose of Naloxone HCl for cats?

Reference doses for Naloxone HCl in cats: 0.01–0.04 mg/kg IV q30–60 min as needed (Opioid reversal). Confirm against the label and the patient before use.

### What is the dose of Naloxone HCl for horses?

Reference doses for Naloxone HCl in horses: 0.01–0.04 mg/kg IV q30–60 min as needed (Opioid reversal (esp. butorphanol / morphine sedation)). Confirm against the label and the patient before use.

### When should Naloxone HCl not be used?

Known hypersensitivity. Caution: full reversal of analgesia in animals with severe pain is contraindicated — titrate to respiratory effort only. Withdrawal seizures in opioid-dependent patients (rare in veterinary practice).

### What are the side effects of Naloxone HCl in animals?

Acute pain crisis (rapid full reversal of analgesia); Tachycardia / hypertension; Tremor / hyperalgesia; Vomiting (sudden return of GI motility).

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.