PetMD Editorial
By PetMD Editorial
Published: November 7, 2012

Drug Info

  • Common Name: Promace, Aceproject, Aceprotabs, ACE
  • Drug Type: Tranquilizer/Sedative
  • Used For: Motion Sickness
  • Species: Dogs, Cats, Horses
  • Available Forms: 5mg, 10mg, and 25mg Tablet, Injectable
  • FDA Approved: Yes

What Is Acepromazine?

Acepromazine is a commonly used tranquilizer/sedative in dogs, cats, horses, and other animals. Veterinarians typically prescribe acepromazine to quiet agitated animals or use it as a part of an anesthetic protocol. It is important to note that when used alone, acepromazine is not an effective pain reliever and does little if anything to relieve a pet’s anxiety or fear. Acepromazine can also be used to treat motion sickness and nausea associated with car or plane rides.

The drug’s effect typically lasts six to eight hours but may be prolonged in certain cases. Give acepromazine 30 to 60 minutes before you need your pet to be sedated.


How It Works

The mechanism by which acepromazine decreases a pet’s alertness is not fully understood. It is thought to block dopamine receptors in the brain or inhibit the activity of dopamine in other ways.


Storage Information

Store in a tightly sealed container at room temperature and away from bright light and moisture.


Acepromazine Dosage

Appropriate dosages for acepromazine depend on a pet’s size, breed, health, and the reason and route that the drug is being given. Follow your veterinarian’s dosing instructions. If you have any questions or concerns, contact your veterinarian before giving the medication. The dosages that are included on acepromazine package inserts are far too high for most animals under typical circumstances.

What to Do If You Miss a Dose

Give the dose as soon as possible. If it is almost time for the next dose, skip the missed dose and continue with the regular schedule. Do not give your pet two doses at once. Call your veterinarian if you have any questions.

Side Effects 

Acepromazine is associated with certain recognized side effects. Veterinarians used to warn against its use in animals who are prone to seizures, but recent research shows that it is probably safe under these circumstances. Side effects that owners should be aware of include:

  • Exposure of your pet’s "third eyelid"
  • Low blood pressure
  • Reduced respiratory rate
  • Discoloration of the urine (pink or brown)
  • Aggression
  • Protrusion of the penis in male horses

Potential Drug Reactions


Acepromazine may react with these drugs:

  • Organophosphate insecticides (included in some flea and worm control products)
  • Metoclopramide
  • Opioid pain relievers
  • Acetaminophen
  • Antacids
  • Antidiarrheal drugs like Kaopectate® or Pepto-Bismol®
  • Phenobarbital (and other barbiturate drugs)
  • Phenytoin sodium
  • Propranolol
  • Quinidine

Other drug reactions are also possible. Make sure your veterinarian is aware of any drugs (prescription or over-the-counter), herbal remedies, and supplements that your pet is taking.


Acepromazine can have an extremely variable effect in pets. Individuals may be relatively resistant to the drug or experience profound and/or prolonged sedation with typical dosages. It is best to perform a “trial dose” before a specific event calls for its use. Older animals may be especially prone to prolonged and deep sedation when given acepromazine. Use with caution in pets with kidney disease, liver disease, heart disease, or low blood pressure.

Some breeds are more sensitive to the adverse effects of acepromazine than others. Brachycephalic breeds (e.g., Pugs, Bulldogs, and especially Boxers) and giant breeds may have an increased risk of side effects. Herding dogs like Collies and Australian Shepherds that carry the MDR-1 (also called ABCB1) genetic mutation can be especially sensitive to acepromazine and should usually be given a reduced dosage. On the other hand, Terriers may require more acepromazine than expected to achieve the desired degree of sedation.

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