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Acepromazine for Dogs

Everything You Need to Know About Acepromazine for Dogs

Has your dog ever been prescribed acepromazine? This medication is a tranquilizer generally used to calm down factious or overly active dogs. Acepromazine has been used in humans before, but now it’s almost exclusively used in veterinary medicine for dogs, cats, and horses. Let’s learn more about acepromazine in this article! We’ll define what this medication is and outline its intended effects, uses, dosage, potential adverse effects, contraindications, and interactions with other medicines. We’ll also give you tips on how to care for your dog under acepromazine.

What is Acepromazine?

Acepromazine for dogs Acepromazine is a tranquilizer drug pharmacologically classified under phenothiazine derivatives. This medication is given as a sedative or tranquilizer used in both dogs and cats. Before, acepromazine was used to treat psychosis in humans during the 1950s. However, the medication is now almost exclusively used in veterinary medicine and rarely used in humans. Veterinarians prescribe acepromazine often as part of an anesthesia protocol. The medication is also used to calm down agitated dogs, cats, and horses. Acepromazine’s sedating effects may last 6-8 hours, but the medication’s effects may also wear down easily. Dogs and cats given acepromazine may easily be aroused when given sufficient stimuli. Acepromazine is available in oral and injectable forms. Oral tablets are prescribed to help manage a dog’s agitation due to high-stress events. Meanwhile, the injectable form is given into a muscle or through a vein as part of anesthesia protocols when a dog needs to undergo a surgical procedure. It may also be given intravenously during a dog’s immediate postoperative period as part of the pain management plan.

What Does Acepromazine Do to Dogs?

What does Acepromazine do to dogs? Acepromazine works by inhibiting the dopaminergic receptors in a dog’s brain. These receptors accept dopamine, a hormone and chemical messenger (neurotransmitter) in between brain cells. Dopamine, in turn, is responsible for regulating emotions and reward-motivated behavior.  Specifically, dopamine controls a dog’s motivational salience. This pertains to a cognitive process that motivates a dog’s behavior towards or away from a specific object, outcome, or event. When acepromazine inhibits dopamine receptors in a dog’s brain, it slows down dopamine’s function in the body. The dog’s motivational salience becomes modulated as his bodily functions gradually slow down to a calmer and sedated state. Apart from dopaminergic receptors, acepromazine also blocks the following:
  • Serotonergic-receptors, leading to reduced anxiety and aggression
  • Histaminergic-receptors, resulting in the elimination of nausea and vomiting
  • Alpha 1/Alpha 2-receptors, leading to lowered blood pressure and sedation
Acepromazine’s blocking mechanisms result in its tranquilizing effect on dogs. Acepromazine is metabolized in the liver after entering the body through oral or intravenous means. Its half-life in dogs is 15.9 hours after oral administration and 7.1 hours after intravenous injection, making it a short-acting medication. Acepromazine is finally excreted in the dog’s urine.

Uses of Acepromazine in Dogs

Uses of Acepromazine Veterinarians primarily prescribe acepromazine for sedating dogs. It’s mainly used in conjunction with atropine or other similar medications as preoperative meds for anxiety and dysrhythmia (abnormality in the heart or brain’s rhythm). Acepromazine is typically given as an injection through the dog’s muscle or intravenously. Acepromazine helps maintain a steady anesthesia plane while a dog is undergoing a surgical procedure. The medication also assists the dog in smoothly coming off the anesthesia drugs during the immediate post-operative recovery phase without putting undue stress on the dog’s heart function. Apart from being part of an anesthesia plan, here are other uses of acepromazine in dogs:
  • As a post-operative pain reliever in conjunction with stronger pain relief medications (acepromazine doesn’t work well as a pain reliever on its own)
  • As a preventative drug for motion sickness
  • Given to decrease agitation and control fractious dogs during high-stress events such as during a thunderstorm, a veterinary office visit, or grooming and nail trimming appointment
  • Given to dogs with allergies to temporarily relieve itchiness and scratching
Acepromazine is usually given intravenously as a conjunct medication for relieving postoperative pain. Meanwhile, the drug can be given orally for motion sickness, agitation control, and allergy symptom relief. Note that your dog may still suffer from anxiety at times even if he is well-trained. And by well-trained, we mean he can follow commands, doesn’t beg for food, or bother people and guests [1]. Stressful events may potentially turn him into a fractious dog. As such, medications such as acepromazine can help calm him down.

Acepromazine for Dogs Dosage

Acepromazine dosage for dogs Your veterinarian will determine the most appropriate dosage of acepromazine for your dog. Dosing decisions will be based on your dog’s health condition, his activity levels, how deeply he needs to be tranquilized, and how long he needs to stay sedated. The MSD Veterinary Manual lists the dosing recommendations for acepromazine as follows:
  • 0.05-0.1 mg/kg given either intravenously, intramuscularly, or subcutaneously
  • 0.55-2.2 mg/kg given orally, three times or four times per day
Acepromazine is typically given 45 minutes to an hour before a surgical procedure or an anticipated stressful event. That’s because the drug has a long onset of action. Acepromazine starts working:
  • 15 minutes after intravenous administration
  • 30-45 minutes after intramuscular administration
  • 30 minutes to one hour after oral ingestion
The length of time acepromazine remains therapeutically active in the dog’s body ranges from 3-6 hours after its onset of action. This may also depend on how quickly the dog metabolizes the drug.

Side Effects of Acepromazine

Side effects of Acepromazine Here are the potential side effects your dog might experience while using acepromazine:
  • Low blood pressure (hypotension)
  • Decreased heart rate (bradycardia)
  • Decreased respiratory rate (bradypnea)
  • Temporary color changes in urine, turning it into pinkish or red-brown color
  • Temporary pain at the injection site when given intramuscularly
  • Exposure of the dog’s third eyelid
  • Mild urinary incontinence, especially in spayed female dogs
Meanwhile, some animals may display more agitation and restlessness after receiving acepromazine. This is more often seen in cats, but may also be observed in dogs. More serious side effects may also show up, particularly if your dog has been taking acepromazine for quite some time already. These symptoms include the following:

Lowered Hematocrit Count

Hematocrit refers to the ratio of red blood cell volume to the total blood volume inside the dog’s body. Your dog may experience a dose-dependent lowering of his hematocrit count. Such a reading may suggest an insufficient amount of red blood cells, potentially leading to anemia. This unique side effect is temporary, lasting about 12 hours after administration of acepromazine, and may start showing up within 30 minutes after the medication is given.

Vasovagal Syncope

Syncope refers to a temporary and brief loss of consciousness (fainting). It happens when the brain lacks oxygen due to problems in circulation and the heart itself. Now, vasovagal syncope is fainting due to a problem with the dog’s vagus nerve. This nerve assists in regulating the tension within the blood vessels of the heart.  When your dog is excited or agitated, the heart may beat quickly at a short time as prompted by his brain. His vagus nerve then responds to this by dilating the heart’s blood vessels without a consistent increase in blood flow and heart rate. As this happens, the heart will again respond by suddenly beating slower, causing less blood and oxygen to flow into the dog’s brain. He’ll then eventually faint. Vasovagal syncope is observed mostly when boxer breeds are given acepromazine. That’s why veterinarians may choose to give lower doses or skip giving acepromazine altogether for such breeds of dogs.

Cardiovascular Collapse

Dogs are particularly susceptible to cardiovascular collapse among all other animals who use acepromazine. Low blood pressure is the most significant side effect of acepromazine, and when this is not treated promptly, this can quickly spiral into cardiovascular collapse. The dog’s heart stops beating, eventually shutting down the pulmonary function and leading to death. Cardiovascular collapse is a potential side effect of most anesthetic agents like acepromazine. But this has become increasingly uncommon, thanks to modern technology that enables veterinary staff to monitor heart rate and vital signs of dogs under acepromazine during a procedure. Monitoring equipment can detect lowering blood pressure and give out signals even before a cardiac collapse happens. Hence, the veterinary team can take the necessary actions to wake up the dog before his heart stops beating.

Acepromazine Overdose in Dogs

Acepromazine Overdose in Dogs Although rare, an overdose of acepromazine may still occur especially if the dog receives the drug frequently. Watch out for these signs of overdose:
  • Excessive sedation
  • Poor coordination
  • Unsteady gait
  • Marked slowing of both heart and respiratory rates
  • Pale gums
  • Inability to stand
All these signs may ultimately lead to a sudden seizure, collapse, and death. Your veterinarian will treat an overdose of oral acepromazine by emptying the dog’s stomach first. Supportive care will also be given to treat the symptoms seen in the dog. Meanwhile, other medications that may be given to your dog to treat overdose symptoms include:
  • Diazepam or barbiturates – To treat seizures associated with acepromazine overdose
  • Phenylephrine and norepinephrine – To treat severe hypotension caused by acepromazine

Breeds That Must Avoid or Use Acepromazine with Extreme Caution

Breeds That Must Avoid or Use Acepromazine with Extreme Caution As we mentioned earlier, brachycephalic breeds, especially boxers, should ideally not be given acepromazine due to the high risk of vasovagal syncope, a significant drop in blood pressure, and decreased heart rate. Pugs and bulldogs must be given acepromazine with extreme caution.  Meanwhile, giant breeds and greyhounds may be more sensitive to acepromazine. The medication’s effects may last for 12-24 hours instead of the average 6-8 hours in smaller breeds.  Conversely, small breed dogs such as terriers may require higher doses of acepromazine to achieve the desired sedation. This goes the same for chihuahuas, the world’s smallest dog breed [2]. The veterinarian will assess if it is safe to give higher doses depending on the dog’s health status. Dogs with a mutated ABCB1 (MDR1) gene may have increased sensitivity to certain medications including acepromazine. Affected breeds may include:
  • Collies
  • Shetland Sheepdogs
  • Old English Sheepdogs
  • Australian Shepherds
  • English Shepherds
  • German Shepherds
  • Silken Windhounds
  • Longhaired Whippets
  • Other mixed-breed dogs
Have your dog tested for the mutated gene to be sure, especially if he falls under the breed types enumerated above. Reduced doses of acepromazine may be given to dogs with mutated genes.

When Should Acepromazine Not Be Given to Dogs?

When Should Acepromazine Not Be Given to Dogs? Your veterinarian may not give acepromazine if your dog falls under these precautionary criteria:
  • Dogs that are anemic, dehydrated, or in shock
  • Older dogs
  • Dogs suffering from liver, kidney, heart disease
  • Dogs already suffering from low blood pressure
  • Dogs who are prone to seizures or with a history of epilepsy
  • Dogs receiving a myelogram
  • Pregnant and lactating mother dogs
  • Younger dogs, due to the drug’s ability to alter thermoregulation response
  • Dogs with tetanus or strychnine poisoning

Drug Interactions with Acepromazine

Drug Interactions with Acepromazine Medications that may have interactions with acepromazine include the following:
  • Antacids and antidiarrheals such as Kaopectate and Pepto-Bismol – These medications reduce the absorption of acepromazine in oral form.
  • Phenobarbitals and other barbiturates, opioid pain relievers – Should be given in lower doses to decrease the risk of significant central nervous system depression when used with acepromazine.
  • Deworming agents and organophosphate insecticides – Acepromazine should be avoided within one month after deworming with organophosphates.
  • Metoclopramide – This is a medication used for nausea. Using it with acepromazine leads to potential exacerbation of metoclopramide’s neurological side effects.
  • Acetaminophen – Using acepromazine with acetaminophen can make a dog’s body temperature drop significantly.
  • Epinephrine – A further lowering of blood pressure will occur if epinephrine is used to treat hypotension caused by acepromazine used.
Other drugs that may cause significant interaction with acepromazine are:
  • Phenytoin sodium
  • Quinidine
  • Propranolol
  • Metronidazole
  • Cisapride
Disclose all over-the-counter and prescription medications, herbals, and supplements your dog is taking to your veterinarian. That’s because other drug reactions are still possible.

Caring for Your Dog Taking Acepromazine

Caring for Your Dog Taking Acepromazine Your veterinarian may prescribe oral acepromazine tablets if your dog suffers from a fractious attitude during stressful events. It may also be given to counter motion sickness in traveling dogs. Here’s what you must know about safely giving oral acepromazine to your pet.
  • Always follow your veterinarian’s dosing advice. Never add more doses to the medication simply because you think acepromazine isn’t working for your dog. If you observed that acepromazine is truly not as effective for your dog, tell your veterinarian so that another medication may be prescribed instead.
  • Acepromazine is typically given three or four times a day, depending on the dose. You can give it 30-60 minutes before the stressful triggering event.
  • Give the medication after your dog has already eaten. Food reduces irritation that may occur in your dog’s stomach after acepromazine ingestion.
  • If you missed a dose, give it to your dog as soon as you remember. Refrain from giving the missed dose if it’s almost time for the next dose. Never give two doses of oral acepromazine at once.
  • Support your dog at all times. He’ll be drowsy after acepromazine administration, so keep him safe and secure to avoid accidents.

The Wrap-Up

Acepromazine is a medication used to calm down dogs during stressful events. It’s also given to prepare them for additional anesthesia in the medical setting. It is important to know its mode of action, possible adverse effects, and care tips to ensure that acepromazine safely fulfills its purpose in your dog.


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