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About Acepromazine Dog Tranquilizer

In dogs, acepromazine is frequently prescribed as an anti-anxiety and anti-nausea medication, but is it safe?

Melvin Peña  |  Dec 8th 2015


Fireworks, car travel, veterinary appointments: These are just a few predictable and common occurrences for dog owners. For dogs, they can be sources of overwhelming anxiety. Whether it’s the sudden loud noise of controlled holiday explosives, motion sickness during long trips, or nervous energy that turns into aggressive behavior, dogs can have dramatic and adverse reactions to seemingly mundane stimuli.

If these scenarios are all too familiar to you and your dog, are there reliable medical treatment options? What about acepromazine and other dog tranquilizers? Should prescription medications for humans be a first choice for relieving your dog’s anxiety, or a method of last resort? Let’s look more closely at acepromazine: its history, uses, side effects, and possible complications for our canine companions.

What is acepromazine?

Acepromazine — also known as acetylpromazine, or simply “Ace” — is derived from phenothiazine, a chemical compound which has been used, among other purposes, as an insecticide, an anti-parasitic, and to treat nausea. In the 1950s, acepromazine maleate found wide use in mental health care to treat chronic depression and psychosis in humans. As a psychoactive medication, it was believed to relieve anxiety and calm the nerves. In the 1950s, a number of other techniques were fashionable in treating mental illness: things like trans-orbital lobotomies and electroshock therapy.

about acepromazine dog tranquilizer

A visit to the vet can cause anxiety in dogs. (Photo by Austin Community College on Flickr)

Like those innovations, acepromazine soon fell out of medical favor as a treatment for humans. It was too unpredictable in its actions, and patients in clinical trials developed addictions to it. While the drug has sedative properties, researchers found that the drug did not relieve symptoms as much as it masked them. By the end of the decade, clinical studies were concluding that acepromazine was ineffective, and quite possibly hazardous, to humans.

About acepromazine dog tranquilizer

Subsequently, acepromazine found use in veterinary practice as an anti-anxiety medication for larger animals like horses, but also dogs and cats. Since it affects multiple organs and systems in a dog’s body — from the brain and heart to the liver — acepromazine is one of the most powerful veterinary drugs currently in use.

It’s surprising, given its volatility and strength, that acepromazine is frequently described as one of if not the most commonly used tranquilizer in veterinary medicine. Why do household pets require such strong sedatives? For some skittish dogs, particularly in urban areas where construction, celebrations, or crowds tend to be large and chaotic but predictable, medication provides a reliably calming influence. It is also used as a pre-operative anti-anxiety medication for dogs who experience major anxiety or aggression at vets’ offices.

While acepromazine is not prescribed for people anymore, its sedative properties subsequently found use in veterinary practice. Prescribed off-label as a tranquilizer, it is used to quell anxiety and nausea in dogs, cats, and horses. These reactions may be caused by any of the scenarios described above. Acepromazine is used to calm dogs who have low tolerance for sudden, loud noises such as those heard during fireworks displays and thunderstorms, to suppress travel sickness, and to quell aggression for animals in unfamiliar or threatening social situations.

How does acepromazine work?

From the 1950s up to the present day, no one — not psychologists, researchers, nor veterinarians — has figured out precisely how acepromazine works. The results of its use are observable — for instance, it is known that its effects take about 45 minutes to kick in and last from six to eight hours — but the actual mechanics of the drug are not fully understood. Its major function is to block or inhibit dopamine receptors in the brain.

about acepromazine dog tranquilizer

Motion sickness in dogs can be problematic. (Photo via Wikimedia Commons)

Dopamine is a chemical that not only affects perception of pain and pleasure, but it also plays vital roles in basic motor function and in the ways that digestive systems function. Blocking these receptors may make people — or animals — seem calmer, but even as a veterinary drug, Ace has been criticized in recent years because a peaceful exterior appearance does not always translate to a settled mind.

It certainly slows the heart rate and decreases blood pressure. The drug also impairs motor function and self-regulatory functions, including body temperature and reaction times. Though it is used as an anti-anxiety medication, there are indications that while it may stabilize heart function, it does not actually suppress anxiety. In other words, a dog’s mind may still be panicked, but his body may be rendered unable to react. 

Acepromazine dosage for dogs

Physically, dogs come in such a wide variety of sizes, breeds, and mixes, to say nothing of their individual temperaments, that dosing a particular dog with acepromazine remains a matter of trial and error. In tablet form, the drug is absorbed into the bloodstream less consistently than it is by injection. Lower doses are given for pre-operation sedation, but for other uses, vets tend to determine dosage by how a specific dog responds.

about acepromazine dog tranquilizer

Some dogs aren’t so stoic during thunderstorms. (Photo via Shutterstock)

Acepromazine side effects

The side effects of acepromazine in dogs are unpredictable, it interacts poorly with a number of other veterinary drugs, and certain breeds are cautioned not to use it at all. Because it affects heart function and requires the liver to process and metabolize it, dogs who have been diagnosed with heart and liver disorders are strongly cautioned against using acepromazine.

Instead of soothing anxiety or nerves in dogs, it may make them more sensitive to loud noises. Dogs who are prone to seizures are at increased risk while taking acepromazine. There are certain dog breeds, among them various sighthounds and those with shorter muzzles, who are at risk because decreased blood and oxygen flow makes temperature regulation and breathing more difficult. Specific breed clubs, like the American Boxer Club, have had warnings about acepromazine‘s negative impact posted since the late 1990s.

How do you calm your anxious dogs?

The mental health of our dogs isn’t a topic that receives as much attention as it could or should. Physically and emotionally, the average dog enjoys and benefits from regular attention, affection, and exercise. The three in combination tend to keep most dogs healthy and well-adjusted.

However, even the most assiduous and proactive dog owners can reach their wits’ end when it comes to a reactive pet. Does your dog suffer regularly from anxiety or nausea? What natural methods do you employ to soothe them? What medications does your veterinarian prescribe?

About the author: Melvin Peña trained as a scholar and teacher of 18th-century British literature before turning his research and writing skills to puppies and kittens. He enjoys making art, hiking, and concert-going, as well as dazzling crowds with operatic karaoke performances. He has a two-year-old female Bluetick Coonhound mix named Baby, and his online life is conveniently encapsulated here.