Acepromazine for Dogs and Cats: Dosing and Effects

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-09-20

Acepromazine is a phenothiazine tranquilizer and dopamine D2 receptor antagonist used in dogs and cats for sedation, as a preanesthetic medication, and as an adjunct to antiemetic therapy. It produces calmness and reduces anxiety and spontaneous movement without providing pain relief. The acepromazine drug is one of the most widely used tranquilizers in small animal practice, valued for its reliability, low cost, and long duration of effect. It is available as an injectable solution and as oral tablets, and it is a prescription-only medication in the United States.

This article covers the pharmacology, labeled indications, dosing, onset and duration, adverse effects, contraindications, drug interactions, and monitoring points for acepromazine in dogs and cats. It is written for veterinary students, technicians, and clinicians who need a source-grounded reference for clinical use.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

At a Glance

What Acepromazine Is and How It Works

Acepromazine belongs to the phenothiazine class of tranquilizers. Phenothiazines were originally developed as antihistamines and antipsychotics in human medicine, and their sedative properties were recognized and adapted for veterinary use. Acepromazine is the most commonly used phenothiazine in small animal practice.

The sedative effect of acepromazine comes primarily from blockade of dopamine D2 receptors in the central nervous system. Dopamine is a neurotransmitter involved in arousal, motor activity, and the vomiting reflex. When acepromazine blocks D2 receptors in the brain, it reduces spontaneous movement, decreases alertness, and produces a state of calmness without loss of consciousness. The animal remains arousable and can be handled, but is less reactive to its surroundings.

Acepromazine also blocks alpha-1 adrenergic receptors. This action is responsible for many of the cardiovascular effects of the drug, particularly vasodilation and hypotension. Alpha-1 blockade relaxes vascular smooth muscle, lowering systemic vascular resistance and blood pressure. This effect is dose-dependent and can be pronounced in some patients.

Additional receptor interactions include blockade of histamine H1 receptors and muscarinic acetylcholine receptors, though these effects are less prominent than the dopamine and alpha-1 actions. The antiemetic effect of acepromazine is mediated through dopamine D2 blockade at the chemoreceptor trigger zone in the brain.

Acepromazine does not produce analgesia. It does not block pain pathways and does not reduce the perception of pain. An animal sedated with acepromazine can still feel pain and may react to painful stimuli, though the reaction may be muted by sedation. This distinction matters in clinical practice because acepromazine should never be used as a substitute for an analgesic when pain is present or expected.

Labeled Indications

Acepromazine is indicated for the following uses in dogs and cats:

Sedation and tranquilization. Acepromazine produces calmness and reduces anxiety in animals that are excitable, nervous, or difficult to handle. It is used for examinations, diagnostic procedures, grooming, and transport.

Preanesthetic medication. Acepromazine is commonly used as part of a premedication protocol before general anesthesia. It reduces anxiety, facilitates handling, and decreases the dose of induction agents required. Studies in dogs have shown that acepromazine combined with other premedications reduces propofol requirements for induction [1][2].

Antiemetic adjunct. Acepromazine has antiemetic properties mediated by dopamine D2 blockade. It is sometimes used to reduce nausea and vomiting, particularly in patients that do not respond to other antiemetics.

Chemical restraint. In aggressive or fractious animals, acepromazine may be used to facilitate safe handling and examination. It is often combined with an opioid for this purpose.

Acepromazine is not indicated for pain management. It is not an analgesic and should not be used alone when pain is present.

Dosing

Dosing of acepromazine varies by species, route, indication, and the clinical judgment of the veterinarian. The doses below are drawn from published clinical studies and standard veterinary references. Doses should always be confirmed against the product label and adjusted for the individual patient.

Dog Doses

The range of published doses for dogs is broad, from 0.005 mg/kg to 0.05 mg/kg intramuscularly or intravenously. Lower doses (0.01 to 0.02 mg/kg) are typically used when acepromazine is combined with other sedatives or anesthetics. Higher doses (0.03 to 0.05 mg/kg) may be used when acepromazine is the primary sedative or when more profound tranquilization is needed.

Cat Doses

Acepromazine is used in cats, but published dose data from controlled studies are more limited than for dogs. The dose range commonly cited in veterinary references is 0.05 to 0.1 mg/kg intramuscularly or intravenously. Oral dosing in cats is less predictable because of variable absorption.

Cats may be more sensitive to the hypotensive effects of acepromazine, and lower doses are often preferred. The drug should be used cautiously in cats with cardiovascular disease, hepatic impairment, or dehydration.

Oral Dosing

Acepromazine is available as oral tablets. Oral absorption is variable and less predictable than injectable administration. The onset of effect after oral dosing is slower and may range from 30 to 60 minutes or longer. Oral transmucosal administration has been studied in dogs and produces measurable sedation within 1 hour [12]. A clinical trial using oral transmucosal acepromazine at 0.05 mg/kg as part of a preappointment protocol with gabapentin and melatonin showed significantly increased sedation scores compared to baseline [13].

Oral acepromazine is often used for at-home sedation before veterinary visits or for travel. The variability in absorption means that the effect may be less reliable than injectable administration, and owners should be counseled accordingly.

Onset and Duration

After intramuscular injection, the sedative effect of acepromazine typically becomes apparent within 15 to 30 minutes. In a study of conscious dogs receiving intravenous acepromazine, mild tranquilization became obvious at 20 minutes and peaked at 30 minutes after injection [8]. The onset after intramuscular injection is similar, though absorption from muscle may add a few minutes.

After oral administration, onset is slower and more variable. Oral transmucosal administration in dogs produced significantly increased sedation scores at 1 hour after dosing [12].

The duration of acepromazine sedation is long. The sedative effect typically lasts 4 to 8 hours, and residual effects may persist longer. In a study of tear production in dogs, acepromazine at 0.015 mg/kg intramuscularly caused a significant decrease in tear production at 20 minutes, 40 minutes, 1 hour, and 2 hours after administration, with recovery by 4 hours [4]. This time course reflects the duration of the drug's peripheral effects and is consistent with the clinical observation that acepromazine sedation lasts several hours.

The long duration of acepromazine is an advantage when prolonged sedation is desired, but it can be a disadvantage when rapid recovery is needed. Animals sedated with acepromazine may remain drowsy for the remainder of the day and should be monitored accordingly.

Cardiovascular Effects

The most significant adverse effect of acepromazine is hypotension. This occurs primarily through alpha-1 adrenergic receptor blockade, which causes vasodilation and a decrease in systemic vascular resistance. The hypotensive effect is dose-dependent and can be pronounced, particularly in animals that are dehydrated, hypovolemic, or have pre-existing cardiovascular disease.

A study in conscious dogs evaluated the hemodynamic effects of progressively increasing intravenous doses of acepromazine (10, 25, 50, and 100 micrograms/kg). All doses significantly decreased stroke index, mean arterial pressure, and arterial oxygen content, with maximum decreases of 16%, 17%, and 21%, respectively. Oxygen delivery index decreased by 26% to 38%, with significant differences at the 50 and 100 microgram/kg doses. Systemic vascular resistance index and heart rate did not change significantly [9].

Another study in dogs found that acepromazine combined with dexmedetomidine caused a significant decrease in systolic arterial pressure at 30 minutes compared to baseline [3]. A study comparing acepromazine-methadone with dexmedetomidine-methadone found that blood pressure decreased in the acepromazine groups following treatment [1].

Oral transmucosal acepromazine at 0.05 mg/kg in dogs significantly decreased heart rate and non-invasive blood pressure at 1 hour after administration compared to controls [12].

These findings underscore the importance of assessing hydration status and cardiovascular function before administering acepromazine. Animals that are dehydrated, in shock, or have significant cardiac disease may not tolerate the hypotensive effects of the drug.

Other Adverse Effects

Hypothermia. Acepromazine impairs thermoregulation by affecting the hypothalamic temperature-regulating center and by causing peripheral vasodilation, which increases heat loss. Animals sedated with acepromazine may become hypothermic, particularly in cool environments or during prolonged procedures. Body temperature should be monitored, and active warming should be provided when needed.

Lowered seizure threshold. The effect of acepromazine on seizure threshold is controversial. Phenothiazines have traditionally been thought to lower the seizure threshold, and acepromazine has been listed as potentially epileptogenic in some references. However, clinical evidence supporting this concern is limited, and many veterinary neurologists do not consider acepromazine to be a significant seizure risk in patients with well-controlled epilepsy. The controversy persists, and many clinicians avoid acepromazine in animals with a history of seizures as a precaution. The decision should be made on a case-by-case basis, weighing the benefits of sedation against the theoretical risk.

Behavioral changes. Acepromazine can cause paradoxical excitement in some animals, particularly cats. Instead of becoming calm, the animal may become more agitated or vocal. This reaction is uncommon but should be recognized.

Prolonged sedation. Because of the long duration of acepromazine, animals may remain sedated for many hours after the procedure is complete. Owners should be informed that their pet may be drowsy for the rest of the day and should be kept in a quiet, safe environment.

Reduced tear production. Acepromazine significantly reduces tear production in dogs. A study measuring Schirmer tear test values found a significant decrease at 20 minutes, 40 minutes, 1 hour, and 2 hours after intramuscular administration of acepromazine at 0.015 mg/kg. When acepromazine was combined with methadone, the reduction in tear production persisted until 8 hours after administration [4]. This effect is relevant for animals undergoing ocular procedures or those with pre-existing dry eye. Lubricating eye ointment should be considered during sedation.

Priapism and penile prolapse. Acepromazine can cause relaxation of the retractor penis muscle, leading to penile prolapse or priapism (persistent erection) in male dogs and horses. This effect is uncommon in dogs but has been reported. If priapism occurs, the drug should be discontinued, and veterinary attention should be sought.

Hypotension-related organ injury. Severe hypotension can reduce perfusion to vital organs, particularly the kidneys. Animals with pre-existing renal disease may be at increased risk.

Breed Sensitivity

Some breeds appear to be more sensitive to the effects of acepromazine than others. Boxers are commonly cited as a breed that may have exaggerated responses to acepromazine, including profound sedation, hypotension, and bradycardia. The mechanism for this sensitivity is not fully understood but may relate to breed-specific differences in autonomic tone or drug metabolism.

Other breeds that have been reported to be sensitive include Greyhounds and other sighthounds, which may have lower body fat and different drug distribution characteristics. Giant breeds may also respond more profoundly to standard doses.

Because of this variability, many clinicians use lower doses in these breeds and titrate to effect. The dose should always be individualized based on the patient's response, and the animal should be monitored closely after administration.

Contraindications and Precautions

Acepromazine should not be used in the following situations:

Hypovolemia or shock. The hypotensive effects of acepromazine can be dangerous in animals that are already hypotensive or have inadequate circulating volume. Acepromazine should be avoided until the animal is stabilized.

Severe cardiovascular disease. Animals with significant cardiac disease, particularly those with outflow tract obstruction or arrhythmias, may not tolerate the hemodynamic effects of acepromazine.

Severe hepatic impairment. Acepromazine is metabolized in the liver. Animals with severe liver disease may have prolonged effects and increased risk of adverse reactions.

Known hypersensitivity. Acepromazine should not be used in animals with a known allergy to phenothiazines.

Epilepsy (relative contraindication). The seizure threshold controversy means that acepromazine should be used cautiously in animals with a history of seizures. The decision should be individualized.

Very young or very old animals. Neonates and geriatric patients may have altered drug metabolism and may be more sensitive to acepromazine. Lower doses and careful monitoring are advised.

Pregnancy and lactation. The safety of acepromazine in pregnant or lactating animals has not been established. It should be used only when the potential benefit justifies the risk.

Debilitated animals. Animals that are weak, anemic, or debilitated may not tolerate the cardiovascular effects of acepromazine.

Drug Interactions

Acepromazine interacts with several other drugs commonly used in veterinary practice:

Opioids. Acepromazine is often combined with opioids such as morphine, methadone, or hydromorphone for premedication. The combination produces more profound sedation than either drug alone. However, both classes can cause hypotension, and the combination may increase the risk of cardiovascular depression. Studies have shown that acepromazine combined with morphine and midazolam produces intense sedation and reduces propofol requirements for induction [1].

Alpha-2 agonists. Acepromazine combined with dexmedetomidine or medetomidine can produce significant sedation but also increases the risk of hypotension and bradycardia. A study in dogs found that acepromazine combined with dexmedetomidine did not enhance sedation or reduce propofol requirements compared to dexmedetomidine alone [3].

Propofol. Acepromazine reduces the dose of propofol required for induction of anesthesia. A study in Beagle dogs found that acepromazine at 0.02 mg/kg intravenously reduced the propofol induction dose from 4.4 mg/kg (saline control) to 1.7 mg/kg when combined with butorphanol [2].

Antihypertensive drugs. Acepromazine may potentiate the effects of other drugs that lower blood pressure, including ace inhibitors, beta-blockers, and diuretics.

CNS depressants. Acepromazine may potentiate the effects of other central nervous system depressants, including barbiturates, benzodiazepines, and inhalant anesthetics.

Anticholinergics. Acepromazine has some anticholinergic activity, and combining it with other anticholinergic drugs may increase the risk of tachycardia and other anticholinergic effects.

Epinephrine. Acepromazine may reverse the effects of epinephrine, which is relevant in emergency situations where epinephrine is used for cardiovascular support.

Monitoring Points

When acepromazine is administered, the following parameters should be monitored:

Level of sedation. The depth of sedation should be assessed regularly to ensure the animal is adequately calm but not excessively depressed. Sedation scales can be used to standardize assessment.

Heart rate and rhythm. Acepromazine can cause bradycardia or other arrhythmias. Heart rate should be monitored, particularly in animals with pre-existing cardiac disease.

Blood pressure. Because of the risk of hypotension, blood pressure should be monitored when possible, especially in animals receiving acepromazine in combination with other hypotensive drugs or in animals with cardiovascular compromise.

Respiratory rate and effort. Acepromazine can cause respiratory depression, particularly when combined with opioids or other CNS depressants. Respiratory rate and effort should be monitored.

Body temperature. Hypothermia is a common adverse effect. Body temperature should be monitored, and active warming should be provided if needed.

Mucous membrane color and capillary refill time. These provide a quick assessment of peripheral perfusion and can help detect hypotension.

Tear production. In animals undergoing ocular procedures or with pre-existing dry eye, tear production should be assessed, and lubricating ointment should be applied as needed.

Urine output. In animals with renal disease or those receiving prolonged sedation, urine output should be monitored to assess renal perfusion.

Comparison with Alternatives

Acepromazine is one of several sedatives and tranquilizers available for use in dogs and cats. The choice of agent depends on the clinical situation, the desired depth and duration of sedation, the patient's health status, and the availability of monitoring.

Alpha-2 agonists (dexmedetomidine, medetomidine). These drugs produce reliable sedation and analgesia but cause significant cardiovascular effects, including bradycardia and hypertension followed by hypotension. They are reversible with atipamezole, which allows for rapid recovery. Studies comparing acepromazine with dexmedetomidine have shown that dexmedetomidine produces more profound sedation and greater reduction in propofol requirements, but also more cardiovascular depression [7][15].

Benzodiazepines (midazolam, diazepam). These drugs produce muscle relaxation and sedation but are less reliable as sole sedatives in healthy animals. They are often combined with opioids or acepromazine for premedication. A study comparing acepromazine-morphine, midazolam-morphine, and acepromazine-midazolam-morphine found that the triple combination produced the most intense sedation [1].

Opioids (morphine, methadone, hydromorphone). Opioids provide analgesia and sedation but can cause respiratory depression, nausea, and vomiting. They are often combined with acepromazine for premedication.

Gabapentin and melatonin. These oral agents are sometimes used for at-home sedation before veterinary visits. A study using a combination of gabapentin, melatonin, and oral transmucosal acepromazine found significantly reduced stress scores in anxious and aggressive dogs [13].

Azaperone. Azaperone is another butyrophenone tranquilizer used in veterinary medicine. A study comparing azaperone and acepromazine in dogs found that azaperone produced moderate sedation at 20 minutes without inducing bradycardia or clinically significant hypotension [16].

Clinical Relevance, Limitations and Common Mistakes

Acepromazine is a reliable and widely used tranquilizer, but its limitations must be understood for safe clinical use. The drug provides sedation without analgesia, so it should never be used as the sole agent when pain is present or expected. The hypotensive effects of acepromazine can be significant, particularly in animals that are dehydrated, hypovolemic, or have cardiovascular disease. The long duration of action means that animals may remain sedated for many hours, which can be an advantage or a disadvantage depending on the clinical situation.

Common mistakes in the use of acepromazine include:

Using acepromazine as an analgesic. Acepromazine does not relieve pain. Animals undergoing painful procedures need appropriate analgesia, which may include opioids, NSAIDs, or local anesthetics.

Failing to assess hydration and cardiovascular status. Acepromazine should not be given to animals that are dehydrated or hypotensive. A thorough physical examination and, when indicated, blood work should be performed before administration.

Using high doses in sensitive breeds. Boxers, Greyhounds, and other breeds may be more sensitive to acepromazine. Lower doses should be used, and the animal should be monitored closely.

Ignoring the risk of hypothermia. Acepromazine impairs thermoregulation. Animals should be kept warm during and after sedation.

Overlooking the effect on tear production. Acepromazine reduces tear production, which can be problematic for animals with dry eye or those undergoing ocular procedures. Lubricating ointment should be considered.

Assuming oral absorption is reliable. Oral acepromazine has variable absorption and may not produce consistent sedation. Owners should be informed that the effect may be less predictable than injectable administration.

Failing to monitor blood pressure. Hypotension is a common and potentially serious adverse effect. Blood pressure should be monitored when possible, particularly in animals receiving acepromazine in combination with other hypotensive drugs.

Individual cases require veterinary judgment. The information in this article is a guide, not a substitute for clinical assessment.

Frequently Asked Questions

What is acepromazine used for in dogs and cats?

Acepromazine is used for sedation, preanesthetic medication, chemical restraint, and as an antiemetic adjunct. It produces calmness and reduces anxiety but does not provide pain relief.

How long does acepromazine take to work?

After intramuscular injection, acepromazine typically takes effect within 15 to 30 minutes. Oral absorption is variable and onset may be slower.

How long does acepromazine last?

The sedative effect of acepromazine typically lasts 4 to 8 hours, and residual effects may persist longer. Animals may remain drowsy for the remainder of the day.

Is acepromazine a pain reliever?

No. Acepromazine is a tranquilizer, not an analgesic. It does not block pain pathways and should not be used as a substitute for pain medication.

What are the most common side effects of acepromazine?

The most common side effects are sedation, hypotension, hypothermia, and reduced tear production. Less common effects include paradoxical excitement, priapism, and prolonged sedation.

Can acepromazine be given to cats?

Yes, acepromazine is used in cats, but published dose data are more limited than for dogs. Cats may be more sensitive to the hypotensive effects, and lower doses are often preferred.

Why are Boxers sensitive to acepromazine?

Boxers are commonly cited as a breed that may have exaggerated responses to acepromazine, including profound sedation and hypotension. The mechanism is not fully understood, and lower doses are recommended.

Does acepromazine lower the seizure threshold?

The effect of acepromazine on seizure threshold is controversial. Some references list it as potentially epileptogenic, but clinical evidence is limited. Many clinicians avoid it in animals with a history of seizures as a precaution.

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Sources

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2. Effects of intravenous acepromazine and butorphanol on propofol dosage for induction of anesthesia in healthy Beagle dogs.
3. Acepromazine does not enhance sedation or reduce propofol requirements when combined with dexmedetomidine in dogs.
4. Evaluation of Tear Production as Measured by Schirmer Test I in Dogs after Acepromazine and Acepromazine-Methadone Premedication.
5. Sedative and cardiovascular effects of premedication with acepromazine, methadone and dexmedetomidine in sevoflurane-anaesthetized dogs.
6. Medetomidine-vatinoxan-methadone and acepromazine-methadone: comparison of sedative and cardiovascular properties as a preanaesthetic medication in healthy dogs.
7. Comparison between dexmedetomidine and acepromazine in combination with methadone for premedication in brachycephalic dogs undergoing surgery for brachycephalic obstructive airway syndrome.
8. Modulation of nociceptive withdrawal reflexes evoked by single and repeated nociceptive stimuli in conscious dogs by low-dose acepromazine.
9. Hemodynamic, respiratory and sedative effects of progressively increasing doses of acepromazine in conscious dogs.
10. Effects of acepromazine and dexmedetomidine, followed by propofol induction and maintenance with isoflurane anaesthesia, on the microcirculation of Beagle dogs evaluated by sidestream dark field imaging: an experimental trial.
11. Sedative and cardiopulmonary effects of intramuscular combinations of hydromorphone, acepromazine, dexmedetomidine, and glycopyrrolate followed by intravenous propofol and inhalant isoflurane anesthesia in healthy dogs.
12. Oral transmucosal administration of acepromazine to healthy dogs leads to increased sedation scores in a hospital setting.
13. Gabapentin, melatonin, and acepromazine combination prior to hospital visits decreased stress scores in aggressive and anxious dogs in a prospective clinical trial.
14. Effects of acepromazine, xylazine and propofol on spinal reflexes in healthy dogs.
15. Effect of acepromazine or dexmedetomidine associated with methadone on anesthetic induction with propofol at a rate of 1 mg/kg/min in healthy dogs: A randomized clinical trial.
16. Comparison of the Sedative and Cardiovascular Effects of Azaperone and Acepromazine in Dogs.