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ace-PRO-ma-zeen - Pronunciation guide

Brand Names

  • AceProject
  • Acepromazine Maleate Injection
  • Acepromazine Maleate Injection, USP
  • Acepromazine Maleate Tablets
  • Acepromazine Maleate Tablets, USP
  • Aceprotabs


Rx symbolAcepromazine has a depressant effect on the central nervous system, causing sedation, muscular relaxation, and an overall reduction in activity. The rapid action exerts an almost immediate calming effect, with a low order of toxicity, making it one of the most commonly used tranquilizers.


Acepromazine is a rapid-acting tranquilizer used as an aid for controlling fractious horses during examination, treatment, trailer loading, and transportation. Acepromazine is also commonly used in conjunction with local anesthesia for various surgical procedures, including castration, removal of skin tumors, ocular surgery, and neurectomy.

Acepromazine is sometimes prescribed for laminitis because it lowers blood pressure by dilating small blood vessels, thereby improving circulation in the hoof. Some veterinarians prescribe Acepromazine for horses that are prone to tie up as a preventive measure or as a part of treatment.

Dosage and Administration

Prescription medicationAcepromazine
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 0.25-1.0 mg/lb 10 mg/tablet Treatment NA
Oral 0.25-1.0 mg/lb 25 mg/tablet Treatment NA
Intramuscular injection 2-4 mg/100lb 10 mg/ml Treatment NA
Intravenous injection 2-4 mg/100lb 10 mg/ml Treatment NA


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian..
  • Oral tablets are extra-label for horses.
  • The dosage should be adjusted depending on the degree of tranquilization required. IV doses should be administered slowly, and a period of 15 minutes should be allowed for the drug to take full effect.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Side Effects

Paralysis of the retractor penis muscle has been noted with the use of this class of tranquilizers. This risk should be considered prior to the administration of Acepromazine Maleate Injection to male horses. Dosage should be limited to the minimum amount necessary for the desired effect. Note that at the time of administration it is normal to observe the reversible protrusion of the penis. The irreversible paralysis of the retractor penis muscle may occur when a tranquilizer is used in conjunction with testosterone (or in stallions).


Tranquilizers are potent central nervous system depressants and they cause marked sedation with a suppression of the sympathetic nervous system.

If given in excess, tranquilizers can result in depression and motor restlessness that may be amplified in animals that are sensitive to the treatment.

Tranquilizers are additive in action and will increase the effect of general anesthesia. Care should be taken when used in conjunction with general anesthesia, including administration of smaller doses and greater attention to metabolic response.

Animals that are exhibiting symptoms of stress, debilitation, cardiac disease, or shock also require additional care and attention when treated with tranquilizers.

Acepromazine Maleate Injection is detoxified in the liver and must be used with caution in animals with a history of liver dysfunction or leukopenia.

Rapid intravenous injection can result in hypotension, causing cardiovascular collapse. Accidental intracarotid injection can produce clinical signs, ranging from disorientation to convulsive seizures and death.

Acepromazine is FDA approved for use in horses and U. S federal law restricts this drug to use by a lawful written or oral order of a licensed veterinarian.

Acepromazine is a prohibited substance in most sanctioned competitions. It is important to check with the proper regulatory group.


Acepromazine may increase the toxicity of organophosphates. Do not use Acepromazine Maleat Injection to control tremors that result from organic phosphate poisoning. Do not use with procain hydrochloride.


Acute and chronic toxicity studies have shown a very low order of toxicity.


Acepromazine maleate injectionAcepromazine maleate injection

Acepromazine tabletsAcepromazine tablets


Product labels

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About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.