• Commonly prescribed for: Tranquilization
  • Species: Dogs, Cats, and Horses
  • Therapeutic Class: Phenothiazine derivative

Basic Information:

Acepromazine Maleate is a phenothiazine derivative that serves as a popular neuroleptic agent for veterinary use. This tranquilizer operates by decreasing dopamine levels and damping down parts of the reticular activating system, leading to significant sedative effects. The drug is metabolized primarily in the liver and eliminated via the urine.

Uses in Dogs, Cats, and Horses:

  • Dogs and Cats: Acepromazine is extensively used as a pre-anesthetic sedative and for calming animals during events that might cause anxiety such as travel, grooming, or veterinary visits. It is also effective in controlling motion sickness.
  • Horses: It is employed both as a sedative and as part of the treatment regimen for laminitis, a severe inflammation of the hoof. Acepromazine is valued for its ability to improve blood flow due to its vasodilatory effects, and it is sometimes used to manage exertional rhabdomyolysis by decreasing muscle spasms and stress.

Side Effects:

  • Acepromazine can cause hypotension, potentially leading to fainting or collapse, particularly if the animal stands up quickly after lying down. Respiratory and heart rates may decrease, and there may be a significant drop in body temperature, which can be dangerous in very young or debilitated animals.
  • Horses: One notable risk is penile prolapse in stallions, which can become permanent and thus this drug should be used cautiously or avoided in breeding males.


Acepromazine should be used with caution in animals with liver dysfunction, heart issues, or low blood pressure. It is not recommended for use in animals prone to seizures, as it may lower the seizure threshold. Care should be taken in its use with giant dog breeds and brachycephalic breeds due to heightened sensitivity to its cardiovascular effects.

Drug Interactions:

This tranquilizer may interact with various medications, potentially increasing the sedative effects of anesthetics, pain medications, and other sedatives. It may also alter the effects of certain antidiarrheals and antacids which can affect the absorption of orally administered acepromazine.


  • Symptoms of overdose include severe sedation, profound hypotension, respiratory depression, and in extreme cases, collapse or coma. Immediate veterinary intervention is crucial.
  • Treatment typically involves symptomatic support, including fluids and medications to counteract severe drops in blood pressure and manage any seizures that might occur.

Handling and Administration:

  • Acepromazine can be administered orally, intramuscularly, or intravenously, depending on the required speed and duration of effect.
  • The onset and duration of action can vary significantly between the different species and individual animals, making careful dosing and monitoring essential.