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Acepromazine (PromAce)
Revised: March 07, 2023
Published: January 01, 2001

(For veterinary information only)

The size of the tablet/medication is NOT an indication of a proper dose. Never administer any drug without your veterinarian's input. Serious side effects or death can occur if you use drugs on your pet without your veterinarian's advice. 

It is our policy not to give dosing information over the internet.

Brand Name:  PromAce, Aceprotabs

Available in 10 mg, 25 mg tablets, and injectable

How this Medication is Used

Although acepromazine has several actions that might be useful, it is mostly used as a tranquilizer. Strong anti-nausea properties make this medication an excellent choice for traveling pets who are prone to both excessive restlessness and motion sickness.

Acepromazine also can stabilize the rhythm of the heart in certain situations, meaning that it can slow the heart rate or prevent a fear-induced excessively rapid heart rate. This is especially helpful for highly sensitive patients who get so frightened they can actually suffer a "heart attack" from fear.

Acepromazine is commonly used to prepare animals for general anesthesia.

Acepromazine is also classified as an antihistamine; however, due to its strong tranquilizing properties, it would not be used as such.

There is some controversy about the use of this medication in situations that stimulate a panic reaction (thunderstorms, fireworks, etc.). While acepromazine makes patients drowsy, there is some thinking that it heightens the perception of loud noises. Many behaviorists feel that other medications, such as alprazolam or dexmedetomidine, may be superior in these situations though acepromazine has certainly been the mainstay for pet tranquilization for decades.

In summary, acepromazine is used for:

  • Tranquilization
  • Motion sickness

Acepromazine is given 30 to 60 minutes before the triggering event. Often a range of dosing is recommended such that if a lower dose is ineffective after a specific time period, more can be given. Be sure to follow your veterinarian's recommendation on dosing.

Side Effects

Acepromazine is a long-lasting tranquilizer. It should be expected to last 6 to 8 hours.

In extremely rare instances, some pets exhibit aggressive behavior as a reaction to acepromazine.

Acepromazine drops blood pressure by dilating blood vessels. The strong tranquilization effect precludes the use of acepromazine in the treatment of high blood pressure.

Dogs and cats on acepromazine typically bring up their third eyelids. Many pet owners are unaware that their pet has an extra eyelid so we have included the photo. There are no negative effects when this third eyelid is seen but it is helpful to the owner to recognize this side effect so as not to become alarmed.

Prolapsed Third Eyelid in a Cat
Image courtesy of MarVistaVet.

Many dogs of herding breed (especially collie) heritage have been found to have a mutant gene called the MDR-1 mutation. This gene codes for what is called the "P-glycoprotein." The P-glycoprotein is involved in keeping certain biochemicals/drugs OUT of certain body tissues. Dogs with mutant P-glycoproteins, allow more biochemicals/drugs INTO certain body tissues. In the case of acepromazine, dogs with this mutation will be sensitive to acepromazine and become more sedated than expected. Dose adjustments would be required. There is now a test for the MDR-1 mutation so that these dogs can be identified. This is a DNA test using an oral swab. Test kits can be ordered directly from the Washington State University Veterinary School.

Acepromazine use can impart a pinkish or even brownish-red color to urine. This is normal and is of no harm or significance.

Interactions with Other Drugs

Acepromazine should not be used with organophosphate insecticides. This type of insecticide is not commonly used anymore but might be expected in certain types of flea collars and in outdoor flea treatment products. If you are not sure if an insecticide is an organophosphate-based, please ask your veterinarian. A full month is recommended between the use of acepromazine and any organophosphate parasite/insecticide products.

Giving acepromazine in conjunction with antacids will decrease the effect of acepromazine.

Using acepromazine with the heart medication quinidine could lead to negative heart reactions. Heart rhythm disturbances can result when acepromazine is used at the same time as cisapride, ondansetron, or metronidazole.

Concurrent use of acepromazine and metoclopramide (a nausea medication) can enhance the potential for neurologic side effects of metoclopramide.

Combining acepromazine with opiates can lead to a significant drop in blood pressure

Combining acepromazine with acetaminophen can lead to a significant drop in body temperature.

Concerns and Cautions

  • Tablets should be stored at room temperature where they are not exposed to light.

  • If you miss a dose, do not double up on the next dose. Simply give it when you remember to or pick it up with the next dose, allowing at least the proper interval between doses according to the label instructions.

  • Acepromazine is not consistently absorbed into the body when given orally. This means that some pets are hardly tranquilized while others are heavily sedated. More consistent results are obtained with the injectable product.

  • Acepromazine is best not used in patients where circulation is in question. Acepromazine dilates blood vessels, which leads to a drop in blood pressure. Injured patients or patients in shock should not have this medication.

  • Historically, acepromazine has been said to lower the threshold of seizures, and for decades, it has been recommended to avoid acepromazine in patients with known seizures. More recent scrutiny has called this dogma into question and there appears to be no additional seizure risk with the use of acepromazine.

  • Acepromazine should not be used in anemic patients. By dilating the blood vessels in the spleen, acepromazine use leads to increased red blood cell storage in the spleen, leading to an approximately 5% drop in red cell count. This is not important in normal pets but if there has already been a blood loss, this drop in red cell count could be significant.

  • Acepromazine should not be used in patients with known liver disease. Acepromazine is removed from the body by the liver, and if the liver is not working, tranquilization can be markedly prolonged.

  • Sighthounds such as greyhounds, whippets, Salukis, wolfhounds, etc., are sensitive to the effects of acepromazine. A different medication may be a better choice.

Acepromazine may take 30-60 minutes to take effect

Are Boxers Sensitive to Acepromazine Side Effects?

The answer is that no one knows for sure, as no hard proof or scientific studies are available for review. Several anecdotal reports exist of boxers dangerously dropping their heart rates after routine doses of acepromazine. Dose reductions are frequently recommended for this breed in an effort to be prudent. Selecting a different tranquilizer should avoid the issue altogether.

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