# Azaperone: veterinary dose and monograph

> Azaperone is a veterinary sedative or anaesthetic agent. A butyrophenone neuroleptic (tranquilliser) developed for PIGS (Stresnil) — its main uses are calming/sedation to PREVENT AGGRESSION and fighting when mixing or regrouping unfamiliar pigs (and sows to accept piglets), reducing… Indications include prevention of aggression/fighting when mixing or regrouping pigs; promotion of sow acceptance of piglets / reduction of savaging; sedation/tranquillisation for transport, handling and minor procedures in pigs. This monograph lists 2 reference doses for pigs, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

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

## At a glance

- **Drug class:** Sedative / anaesthetic
- **Also known as:** Stresnil, Azaperone
- **Species with doses:** Pigs
- **General dose range:** 1–8 mg/kg IM single dose — check the species tables for the indication
- **Routes:** IM
- **Last reviewed:** 1 October 2026

## Indications

- Prevention of aggression/fighting when mixing or regrouping pigs
- Promotion of sow acceptance of piglets / reduction of savaging
- Sedation/tranquillisation for transport, handling and minor procedures in pigs
- Premedication / restraint (with ketamine); wildlife immobilisation

## Azaperone 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.

### Pigs

*Azaperone doses for pigs*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Aggression on mixing / sow aggression | 2–2.2 mg/kg | IM | single dose | — | Withdrawal NOT established — treat as extra-label |
| Stress / transport / obstetrics / premedication | 0.4–2 mg/kg | IM | single dose | — | Withdrawal NOT established — treat as extra-label |

- Aggression on mixing / sow aggression: Plumb’s p.133: 2 mg/kg (1 mL per 20 kg) deep IM directly behind the ear (UK label); 2.2 mg/kg deep IM for mixing feeder/weanling pigs (former US label). Keep pigs undisturbed during the ~20 min onset. Follow the local label withdrawal.
- Stress / transport / obstetrics / premedication: Plumb’s p.133 (UK label, IM behind the ear): stress 1–2 mg/kg; boar transport 1 mg/kg; weaner transport 0.4–2 mg/kg; obstetrics 1 mg/kg; premedication 1–2 mg/kg. Neither Papich 5e nor Plumb’s gives the higher 4–8 mg/kg restraint doses. Follow the local label withdrawal.

### Wildlife

*Azaperone doses for wildlife*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| 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: Plumb’s mentions that azaperone is part of the BAM (butorphanol–azaperone–medetomidine) combination for cervids but gives no dose (and notes it may add hypoxia risk); Papich 5e has no monograph. Use a wildlife immobilisation reference.

## Contraindications

HORSES, especially stallions (hypotension; persistent penile prolapse/paralysis). Severe cardiovascular compromise/shock (alpha-blockade hypotension). Use as a sole agent for painful procedures (limited analgesia). Excitement/noise during onset (handle quietly). Known hypersensitivity. Observe meat withdrawal in pigs.

## Species-specific warnings

> **Caution:** Horses: Contraindicated — azaperone can cause severe hypotension and persistent penile prolapse/paraphimosis in horses (especially stallions).

## Adverse effects

- Hypotension (alpha-adrenergic blockade)
- Sedation/ataxia; occasional excitement during onset (keep quiet)
- Hypothermia; salivation
- Penile prolapse (a hazard chiefly in horses — contraindicated there)

## Drug interactions

- Other CNS depressants/anaesthetics (ketamine): additive sedation (often combined deliberately)
- Other hypotensive agents: additive hypotension
- Adrenaline: alpha-blockade can produce paradoxical hypotension (avoid adrenaline reversal)

## Pregnancy and lactation

Used in sows (including to aid piglet acceptance); follow label. Avoid unnecessary use late in pregnancy.

## Monitoring

- Sedation level and aggression control (mixing) — keep the group quiet during onset
- Blood pressure/perfusion (hypotension)
- Temperature (hypothermia)
- Meat withdrawal compliance

## Toxicity and overdose

Overdose causes excessive sedation, hypotension, hypothermia and ataxia. In horses (where it is contraindicated) it can cause severe hypotension and persistent penile prolapse/paraphimosis. Otherwise a reasonable margin in pigs.

Management: No specific antidote. Supportive — IV fluids for hypotension (do NOT use adrenaline, which can worsen hypotension via unopposed beta effects given the alpha-blockade; use a direct alpha-agonist like phenylephrine if a pressor is needed), keep warm and quiet. Effects resolve with time.

## Clinical pearls

- The classic "mixing pigs" drug — IM azaperone calms regrouped/unfamiliar pigs and reduces fighting, and helps sows accept piglets; keep the group quiet during the ~20-minute onset
- NOT for horses — risk of severe hypotension and penile prolapse/paralysis (especially stallions)
- Provides tranquillisation, not analgesia — combine with ketamine/analgesics for painful procedures
- If a pressor is needed for hypotension, use a direct alpha-agonist (phenylephrine), not adrenaline (alpha-blockade)

## Mechanism of action

A butyrophenone that antagonises central dopamine (D2) receptors, producing neuroleptic tranquillisation, reduced motor/aggressive activity and an anti-emetic effect, with limited analgesia. Peripheral alpha-adrenergic blockade causes vasodilation/hypotension (and, in horses, smooth-muscle relaxation leading to penile prolapse). The dopaminergic calming underlies its anti-aggression use when pigs are mixed.

## Formulations and products

- Injection 40 mg/mL (Stresnil)
- Stresnil (Elanco (Janssen)) — 40 mg/mL, IM injection

## Storage

Injection: 15–30 °C, protect from light; do not freeze.

## 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.

## Other sedatives and anaesthetics

- [Acepromazine](https://vetmasterji.com/drugs/acepromazine)
- [Alfaxalone](https://vetmasterji.com/drugs/alfaxalone)
- [Detomidine](https://vetmasterji.com/drugs/detomidine)
- [Dexmedetomidine](https://vetmasterji.com/drugs/dexmedetomidine)
- [Diazepam](https://vetmasterji.com/drugs/diazepam)
- [Etomidate](https://vetmasterji.com/drugs/etomidate)
- [Guaifenesin (GGE)](https://vetmasterji.com/drugs/guaifenesin)
- [Isoflurane](https://vetmasterji.com/drugs/isoflurane)

## Frequently asked questions

### What is the dose of Azaperone for pigs?

Reference doses for Azaperone in pigs: 2–2.2 mg/kg IM single dose (Aggression on mixing / sow aggression); 0.4–2 mg/kg IM single dose (Stress / transport / obstetrics / premedication). Confirm against the label and the patient before use.

### Can Azaperone be given to wildlife?

Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species (No reference dose for this species).

### What is the withdrawal period for Azaperone?

Pigs, IM (Aggression on mixing / sow aggression): Withdrawal NOT established — treat as extra-label; Pigs, IM (Stress / transport / obstetrics / premedication): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Azaperone not be used?

HORSES, especially stallions (hypotension; persistent penile prolapse/paralysis). Severe cardiovascular compromise/shock (alpha-blockade hypotension). Use as a sole agent for painful procedures (limited analgesia). Excitement/noise during onset (handle quietly). Known hypersensitivity. Observe meat withdrawal in pigs.

### What are the side effects of Azaperone in animals?

Hypotension (alpha-adrenergic blockade); Sedation/ataxia; occasional excitement during onset (keep quiet); Hypothermia; salivation; Penile prolapse (a hazard chiefly in horses — contraindicated there).

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- 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.