Acepromazine Maleate

Acepromazine maleate is a phenothiazine tranquilizer used to make animals quieter and easier to handle and to support balanced anesthesia. Its principal veterinary roles are short-term chemical restraint and preanesthetic medication in dogs, cats and horses; other species have specific regimens. It can reduce the amount of general anesthetic required when incorporated into a suitable protocol.

Tranquilization can persist beyond the apparent peak effect and varies with the individual and route. Acepromazine does not provide analgesia, and reduced movement does not necessarily mean relief of fear. Its peripheral vascular effects also explain its use as an adjunct in some equine laminitis protocols.

Group

Phenothiazine tranquilizer; sedative; preanesthetic adjunct

Mechanism of Action

Acepromazine blocks dopamine receptors in the central nervous system, reducing dopaminergic activity involved in arousal and producing tranquilization and sedation. Dopamine-receptor blockade in the chemoreceptor trigger zone also contributes to its antiemetic action in small animals. These effects do not interrupt nociceptive transmission sufficiently to provide clinical analgesia.

Blockade of alpha-1 adrenergic receptors prevents norepinephrine-mediated contraction of vascular smooth muscle. The resulting vasodilation lowers peripheral vascular resistance and may reduce blood pressure. In horses, this action can increase digital and laminar blood flow, providing the pharmacologic rationale for its use as a laminitis adjunct.

Acepromazine also has antimuscarinic activity and adds to the effects of other sedatives and anesthetics. Consequently, a quieter patient may require less induction or maintenance anesthetic, while vasodilation and central depression remain relevant components of the combined response.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.025–0.1 mg/kg	IM, IV, SC	Once	Maximum 3 mg/dose; The lower end is commonly sufficient; assess cardiovascular status.
Sedation	0.5–2.2 mg/kg	PO	Every 6–8 h	Oral tranquilization may be prolonged and less predictable than injection.
Anesthetic premedication	0.01–0.05 mg/kg	IV	Once	Administer as part of a multimodal anesthetic plan.
Anxiety associated with pain	0.05 mg/kg	IM, IV, SC	Once	Maximum 1 mg/dose; Do not use in: Shock or significant hypotension; Adjunct to appropriate analgesia; tranquilization does not treat the pain itself.
Anesthetic premedication	0.03–0.05 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Allow time for the sedative effect before induction.
Sedation	0.025–0.2 mg/kg	IV		Maximum 3 mg/dose; Separate restraint regimen; give slowly and allow onset before redosing.
Sedation	0.1–0.25 mg/kg	IM		Separate restraint regimen; assess cardiovascular response.
Anesthetic premedication	1–3 mg/kg	PO		Give at least one hour before surgery; oral response is less reliable.
Anesthetic premedication	0.1–0.2 mg/kg	IV, IM		Maximum 3 mg/dose; Distinct higher premedication range; additive effects with other anesthetic agents.
Morphine-associated premedication	0.05 mg/kg	IM		Combination protocol: acepromazine 0.05 mg/kg IM with morphine 0.5 mg/kg IM; evaluate the combined sedative and cardiovascular effects.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.025–0.1 mg/kg	IM, IV, SC	Once	Assess cardiovascular status before administration.
Sedation	1.1–2.2 mg/kg	PO	Every 6–8 h	Oral tranquilization may be prolonged and less predictable than injection.
Anesthetic premedication	0.01–0.05 mg/kg	IV	Once	Administer as part of a multimodal anesthetic plan.
Anxiety associated with pain	0.05 mg/kg	IM, IV, SC	Once	Maximum 1 mg/dose; Do not use in: Shock or significant hypotension; Adjunct to appropriate analgesia; tranquilization does not treat the pain itself.
Sedation	0.05–0.1 mg/kg	IV		Maximum 1 mg/dose; Separate restraint/sedation regimen; administer slowly.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Sedation	0.04–0.1 mg/kg	IM	Every 36–48 h	Avoid routine redosing at short intervals; penile prolapse may occur.
Perioperative tranquilization	0.01–0.05 mg/kg	IM, SC, IV	Once
Laminitis adjunct	0.04 mg/kg	IV		Adjunct to comprehensive laminitis treatment; no analgesic effect.

Cattle

Use / stage	Dose	Route	Instructions
Tranquilization	0.13–0.26 mg/kg	PO
Tranquilization	0.03–0.1 mg/kg	IM
Tranquilization	0.01–0.02 mg/kg	IV
Tranquilization	0.05–0.1 mg/kg	IV, IM, SC	Separate alternative regimen; not a substitute for analgesia.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.03–0.2 mg/kg	IV, IM, SC	Once	Adult pigs.
Ketamine-associated immobilization	0.5 mg/kg	IM		Combination protocol: acepromazine 0.5 mg/kg IM, then ketamine 15 mg/kg IM after 30 minutes; atropine 0.044 mg/kg IM is described to reduce secretions.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.05–0.1 mg/kg	IM		Do not use in: Shock or significant hypotension; Monitor recumbency, temperature and circulation; an animal-specific food withdrawal interval is not established here.

Goats

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.05–0.1 mg/kg	IM		Do not use in: Shock or significant hypotension; Monitor recumbency, temperature and circulation; an animal-specific food withdrawal interval is not established here.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.1–0.25 mg/kg	IM, SC		Do not use in: Shock or significant hypotension; Hypothermia and hypotension can occur; dehydration increases risk.
Tranquilization	0.25–0.75 mg/kg	IM, SC		Distinct higher-dose alternative; dehydration increases concern about hypotension.

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	1 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Reported onset about 10 minutes and duration 1-2 hours; no analgesia.
Anesthetic premedication	0.1–0.5 mg/kg	SC	Once	Do not use in: Shock or significant hypotension; Allow effect before induction; monitor temperature and perfusion.
Anesthetic premedication	0.25–2 mg/kg	IV, IM, SC		Separate premedication range; administer 15 minutes before induction. It provides no analgesia; monitor hypotension and hypothermia.

Mice

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.5 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Small-mammal regimen; monitor temperature and perfusion.

Rats

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.5 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Small-mammal regimen; monitor temperature and perfusion.

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.5 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Small-mammal regimen; monitor temperature and perfusion.

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.5 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Small-mammal regimen; monitor temperature and perfusion.

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Tranquilization	0.5 mg/kg	IM	Once	Do not use in: Shock or significant hypotension; Small-mammal regimen; monitor temperature and perfusion.

Indications

Short-term sedation and chemical restraint in dogs, cats, horses and selected other species for handling, examination and minor procedures.
Preanesthetic medication and adjunctive tranquilization during balanced anesthesia, reducing the requirement for concurrent induction and maintenance agents.
Antiemetic treatment in selected small-animal patients through dopamine-receptor blockade.
Adjunctive peripheral vasodilation in equine laminitis to increase digital blood flow.
Adjunctive tranquilization when agitation accompanies a painful condition, as part of a treatment plan that includes analgesia.

Contraindications

Avoid in animals with previous phenothiazine-induced dystonia or extrapyramidal reactions.
Hypotension, hypovolemia and cardiovascular compromise increase the risk from vasodilation.
ABCB1-deficient dogs can develop deeper, prolonged sedation; reduce exposure or select an alternative.
Brachycephalic dogs may develop pronounced vagal effects.
Penile prolapse and persistent paraphimosis are important risks in male horses.
A seizure history warrants individual assessment; a consistent increase in clinical seizure risk has not been established.
Administer IV doses slowly. Intra-arterial administration in horses can cause severe CNS effects, seizures and death.
Tetanus or strychnine poisoning increases concern about extrapyramidal effects.
Very young, geriatric, debilitated or hepatically impaired animals may require smaller doses and prolonged observation.
Do not use in gerbils.
Restraint can be unreliable in aggressive animals; sensory stimulation may provoke a sudden response despite apparent tranquilization.

Interactions

Other sedatives and general anesthetics have additive effects.
Vasodilators and hypotensive agents can increase blood-pressure reduction.
Epinephrine or ephedrine may produce unopposed beta effects and worsen hypotension after alpha blockade; dopamine pressor effects may also be reduced.
Metoclopramide can increase extrapyramidal adverse effects.
Organophosphate insecticides or anthelmintics may have potentiated toxicity.
Antacids and adsorbent antidiarrheal mixtures can reduce oral absorption.
Concurrent paracetamol may increase hypothermia risk; opioids can intensify hypotension.

Adverse effects

Sedation, ataxia and hypothermia.
Hypotension and occasionally excessive vagal tone.
Paradoxical excitement, disinhibition or aggression.
Rare dystonia or other extrapyramidal effects.
Penile prolapse or persistent paraphimosis in horses.
Reduced tear production has been observed in cats.
Splenic red-cell sequestration can decrease hematocrit and should be considered when interpreting laboratory results.
Transient injection-site pain and third-eyelid protrusion.
Urine may develop a pink or red-brown discoloration from metabolites.

Toxicity

Excessive exposure can cause prolonged CNS depression and clinically important hypotension. Support perfusion and monitor temperature, ventilation and blood pressure; ABCB1 deficiency can prolong recovery.

Preparations

Preparation	Form	Strength	Route
PromAce Injectable 10 mg/mL Strength is expressed as acepromazine maleate. Protect from light; keep injection from freezing.	Injection	10 mg / mL	IV, IM, SC
PromAce Tablets 10 mg Strength is expressed as acepromazine maleate. Store in a tightly closed container protected from light. Verified equal quarters.	Tablet	10 mg / tablet	PO
PromAce Tablets 25 mg Strength is expressed as acepromazine maleate. Store in a tightly closed container protected from light. Verified equal quarters.	Tablet	25 mg / tablet	PO

Monitoring and Administration

It has no analgesic action, so painful procedures require additional analgesia.

Sedation can outlast the apparent initial response. Blood pressure is an important monitoring endpoint, particularly in compromised patients.

In horses, onset after IV administration may take about 15 minutes, with peak tranquilization at 30-60 minutes; avoid premature redosing. Hepatic metabolism can contribute to prolonged effects in compromised patients.

Monitoring includes tranquilization depth, heart rate and rhythm, blood pressure and body temperature. In male horses, confirm penile retraction and check for injury.

Reproductive safety varies by species and stage of pregnancy; evidence of use in one species does not establish safety in all breeding animals.

A separate equine neuroleptanalgesia description pairs acepromazine 0.02 mg/kg with buprenorphine 0.004 mg/kg IV or xylazine 0.6 mg/kg IV; the excerpt does not independently specify the acepromazine route.

Keep in a tightly closed container at room temperature, protected from light. Stability of compounded preparations is not established. Acepromazine does not interfere with canine adrenal-function testing.