Phenothiazine Sedative / Tranquilizer
Highlights Of Prescribing Information
• Negligible analgesic effects
• Dosage may need to be reduced in debilitated or geriatric animals, those with hepatic or cardiac disease, or when combined with other agents
• Inject IV slowly; do not inject into arteries
• Certain dog breeds (e.g., giant breeds, sight hounds) may be overly sensitive to effects
• May cause significant hypotension, cardiac rate abnormalities, hypo- or hyperthermia
• May cause penis protrusion in large animals (esp. horses)
What Is Acepromazine Used For?
Acepromazine is approved for use in dogs, cats, and horses. Labeled indications for dogs and cats include: “… as an aid in controlling intractable animals… alleviate itching as a result of skin irritation; as an antiemetic to control vomiting associated with motion sickness” and as a preanesthetic agent. The use of acepromazine as a sedative/tranquilizer in the treatment of adverse behaviors in dogs or cats has largely been supplanted by newer, effective agents that have fewer adverse effects. Its use for sedation during travel is controversial and many no longer recommend drug therapy for this purpose.
In horses, acepromazine is labeled “… as an aid in controlling fractious animals,” and in conjunction with local anesthesia for various procedures and treatments. It is also commonly used in horses as a pre-anesthetic agent at very small doses to help control behavior.
Although not approved, it is used as a tranquilizer (see doses) in other species such as swine, cattle, rabbits, sheep and goats. Acepromazine has also been shown to reduce the incidence of halothane-induced malignant hyperthermia in susceptible pigs.
Before you take Acepromazine
Contraindications / Precautions / Warnings
Animals may require lower dosages of general anesthetics following acepromazine. Use cautiously and in smaller doses in animals with hepatic dysfunction, cardiac disease, or general debilitation. Because of its hypotensive effects, acepromazine is relatively contraindicated in patients with hypovolemia or shock. Phenothiazines are relatively contraindicated in patients with tetanus or strychnine intoxication due to effects on the extrapyramidal system.
Intravenous injections should be made slowly. Do not administer intraarterially in horses since it may cause severe CNS excitement/depression, seizures and death. Because of its effects on thermoregulation, use cautiously in very young or debilitated animals.
Acepromazine has no analgesic effects; treat animals with appropriate analgesics to control pain. The tranquilization effects of acepromazine can be overridden and it cannot always be counted upon when used as a restraining agent. Do not administer to racing animals within 4 days of a race.
In dogs, acepromazine’s effects may be individually variable and breed dependent. Dogs with MDR1 mutations (many Collies, Australian shepherds, etc.) may develop a more pronounced sedation that persists longer than normal. It may be prudent to reduce initial doses by 25% to determine the reaction of a patient identified or suspected of having this mutation.
Acepromazine should be used very cautiously as a restraining agent in aggressive dogs as it may make the animal more prone to startle and react to noises or other sensory inputs. In geriatric patients, very low doses have been associated with prolonged effects of the drug. Giant breeds and greyhounds may be extremely sensitive to the drug while terrier breeds are somewhat resistant to its effects. Atropine may be used with acepromazine to help negate its bradycardic effects.
In addition to the legal aspects (not approved) of using acepromazine in cattle, the drug may cause regurgitation of ruminal contents when inducing general anesthesia.
Acepromazine’s effect on blood pressure (hypotension) is well described and an important consideration in therapy. This effect is thought to be mediated by both central mechanisms and through the alpha-adrenergic actions of the drug. Cardiovascular collapse (secondary to bradycardia and hypotension) has been described in all major species. Dogs may be more sensitive to these effects than other animals.
In male large animals acepromazine may cause protrusion of the penis; in horses, this effect may last 2 hours. Stallions should be given acepromazine with caution as injury to the penis can occur with resultant swelling and permanent paralysis of the penis retractor muscle. Other clinical signs that have been reported in horses include excitement, restlessness, sweating, trembling, tachypnea, tachycardia and, rarely, seizures and recumbency.
Its effects of causing penis extension in horses, and prolapse of the membrana nictitans in horses and dogs, may make its use unsuitable for show animals. There are also ethical considerations regarding the use of tranquilizers prior to showing an animal or having the animal examined before sale.
Occasionally an animal may develop the contradictory clinical signs of aggressiveness and generalized CNS stimulation after receiving acepromazine. IM injections may cause transient pain at the injection site.
Overdosage / Acute Toxicity
The LD50 in mice is 61 mg/kg after IV dosage and 257 mg/kg after oral dose. Dogs receiving 20-40 mg/kg over 6 weeks apparently demonstrated no adverse effects. Dogs gradually receiving up to 220 mg/kg orally exhibited signs of pulmonary edema and hyperemia of internal organs, but no fatalities were noted.
There were 128 exposures to acepromazine maleate reported to the ASPCA Animal Poison Control Center (APCC; www.apcc.aspca.org) during 2005-2006. In these cases, 89 were dogs with 37 showing clinical signs and the remaining 39 reported cases were cats with 12 cats showing clinical signs. Common findings in dogs recorded in decreasing frequency included ataxia, lethargy, sedation, depression, and recumbency. Common findings in cats recorded in decreasing frequency included lethargy, hypothermia, ataxia, protrusion of the third eyelid, and anorexia.
Because of the apparent relatively low toxicity of acepromazine, most overdoses can be handled by monitoring the animal and treating clinical signs as they occur; massive oral overdoses should definitely be treated by emptying the gut if possible. Hypotension should not be treated with epinephrine; use either phenylephrine or norepinephrine (levarterenol). Seizures may be controlled with barbiturates or diazepam. Doxapram has been suggested as an antagonist to the CNS depressant effects of acepromazine.
How to use Acepromazine
Note: The manufacturer’s dose of 0.5-2.2 mg/kg for dogs and cats is considered by many clinicians to be 10 times greater than is necessary for most indications. Give IV doses slowly; allow at least 15 minutes for onset of action.
Acepromazine dosage for dogs:
a) Premedication: 0.03-0.05 mg/kg IM or 1-3 mg/kg PO at least one hour prior to surgery (not as reliable) ()
b) Restraint/sedation: 0.025-0.2 mg/kg IV; maximum of 3 mg or 0.1-0.25 mg/kg IM; Preanesthetic: 0.1-0.2 mg/kg IV or IM; maximum of 3 mg; 0.05-1 mg/kg IV, IM or SC ()
c) To reduce anxiety in the painful patient (not a substitute for analgesia): 0.05 mg/kg IM, IV or SC; do not exceed 1 mg total dose ()
d) 0.55-2.2 mg/kg PO or 0.55-1.1 mg/kg IV, IM or SC (Package Insert; PromAce — Fort Dodge)
e) As a premedicant with morphine: acepromazine 0.05 mg/kg IM; morphine 0.5 mg/kg IM ()
Acepromazine dosage for cats:
a) Restraint/sedation: 0.05-0.1 mg/kg IV, maximum of 1 mg ()
b) To reduce anxiety in the painful patient (not a substitute for analgesia): 0.05 mg/kg IM, IV or SC; do not exceed 1 mg total dose ()
c) 1.1-2.2 mg/kg PO, IV, IM or SC (Package Insert; PromAce — Fort Dodge)
d) 0.11 mg/kg with atropine (0.045-0.067 mg/kg) 15-20 minutes prior to ketamine (22 mg/kg IM). ()
Acepromazine dosage for ferrets:
a) As a tranquilizer: 0.25-0.75 mg/kg IM or SC; has been used safely in pregnant jills, use with caution in dehydrated animals. ()
b) 0.1-0.25 mg/kg IM or SC; may cause hypotension/hypothermia ()
Acepromazine dosage for rabbits, rodents, and small mammals:
a) Rabbits: As a tranquilizer: 1 mg/kg IM, effect should begin in 10 minutes and last for 1-2 hours ()
b) Rabbits: As a premed: 0.1-0.5 mg/kg SC; 0.25-2 mg/kg IV, IM, SC 15 minutes prior to induction. No analgesia; may cause hypotension/hypothermia. ()
c) Mice, Rats, Hamsters, Guinea pigs, Chinchillas: 0.5 mg/kg IM. Do not use in Gerbils. ()
Acepromazine dosage for cattle:
a) Sedation: 0.01-0.02 mg/kg IV or 0.03-0.1 mg/kg IM ()
b) 0.05 -0.1 mg/kg IV, IM or SC ()
c) Sedative one hour prior to local anesthesia: 0.1 mg/kg IM ()
Acepromazine dosage for horses:
(Note: ARCI UCGFS Class 3 Acepromazine)
a) For mild sedation: 0.01-0.05 mg/kg IV or IM. Onset of action is about 15 minutes for IV; 30 minutes for IM ()
b) 0.044-0.088 mg/kg (2-4 mg/100 lbs. body weight) IV, IM or SC (Package Insert; PromAce — Fort Dodge)
c) 0.02-0.05 mg/kg IM or IV as a preanesthetic ()
d) Neuroleptanalgesia: 0.02 mg/kg given with buprenorphine (0.004 mg/kg IV) or xylazine (0.6 mg/kg IV) ()
e) For adjunctive treatment of laminitis (developmental phase): 0.066-0.1 mg/kg 4-6 times per day ()
Acepromazine dosage for swine:
a) 0.1-0.2 mg/kg IV, IM, or SC ()
b) 0.03-0.1 mg/kg ()
c) For brief periods of immobilization: acepromazine 0.5 mg/ kg IM followed in 30 minutes by ketamine 15 mg/kg IM. Atropine (0.044 mg/kg IM) will reduce salivation and bronchial secretions. ()
Acepromazine dosage for sheep and goats:
a) 0.05-0.1 mg/kg IM ()
■ Cardiac rate/rhythm/blood pressure if indicated and possible to measure
■ Degree of tranquilization
■ Male horses should be checked to make sure penis retracts and is not injured
■ Body temperature (especially if ambient temperature is very hot or cold)
■ May discolor the urine to a pink or red-brown color; this is not abnormal
■ Acepromazine is approved for use in dogs, cats, and horses not intended for food
Chemistry / Synonyms
Acepromazine maleate (formerly acetylpromazine) is a phenothiazine derivative that occurs as a yellow, odorless, bitter tasting powder. One gram is soluble in 27 mL of water, 13 mL of alcohol, and 3 mL of chloroform.
Acepromazine Maleate may also be known as: acetylpromazine maleate, “ACE”, ACP, Aceproject, Aceprotabs, PromAce, Plegicil, Notensil, and Atravet.
Storage / Stability/Compatibility
Store protected from light. Tablets should be stored in tight containers. Acepromazine injection should be kept from freezing.
Although controlled studies have not documented the compatibility of these combinations, acepromazine has been mixed with atropine, buprenorphine, chloral hydrate, ketamine, meperidine, oxymorphone, and xylazine. Both glycopyrrolate and diazepam have been reported to be physically incompatible with phenothiazines, however, glycopyrrolate has been demonstrated to be compatible with promazine HC1 for injection.
Dosage Forms / Regulatory Status
Acepromazine Maleate for Injection: 10 mg/mL for injection in 50 mL vials; Aceproject (Butler), PromAce (Fort Dodge); generic; (Rx). Approved forms available for use in dogs, cats and horses not intended for food.
Acepromazine Maleate Tablets: 5, 10 & 25 mg in bottles of 100 and 500 tablets; PromAce (Fort Dodge); Aceprotabs (Butler) generic; (Rx). Approved forms available for use in dogs, cats and horses not intended for food.
When used in an extra-label manner in food animals, it is recommended to use the withdrawal periods used in Canada: Meat: 7 days; Milk: 48 hours. Contact FARAD (see appendix) for further guidance.
The ARCI (Racing Commissioners International) has designated this drug as a class 3 substance. See the appendix for more information.
Human-Labeled Products: None