ACP: Behavioural Disorders



Effects of acepromazine (acetylpromazine)

Acepromazine is one of the phenothiazine tranquillisers. Its main action is to block dopamine receptors in the brain (dopamine antagonist).

Acepromazine also has anticholinergic, antiserotonergic, adrenolytic and antihistaminic actions. As a tranquiliser, acepromazine has a potent effect in causing a nonspecific reduced responsiveness to external stimuli, decreased spontaneous motor activity and general behavioural quieting. Spinal reflexes remain unchanged. It does not have an anxiolytic effect. (Booth, 1988; Dodman, 1998).


The side-effects of short term use of acepromazine include the following (Booth, 1988; Dodman,1998):

Hypotension (often accompanied by a compensatory tachycardia)
Syncope, particularly in brachycephalic breeds, the Boxer being especially sensitive
Reduction of the seizure threshold
Extrapyramidal signs e.g. ataxia, muscle tremors, incoordination, pacing, agitation

Known symptoms of overdosage

According to the package insert, known symptoms of overdosage include prolonged depression accompanied by psychomotor hyperactivity.


Acepromazine is currenty indicated in dogs and cats for the following uses:

As a premedication for anaesthesia, usually in combination with atropine. Premedication reduces the amount of barbiturate and inhalant anaesthetic needed, and the tranquillising effect makes it easier to administer intravenous anaesthesia.
As a chemical restraint for intractable (difficult to handle) patients, i.e. to calm down excitable patients e.g. to assist in performing diagnostic procedures.
Travel sickness: Acepromazine counteracts emesis due to central action.
Strychnine poisoning in dogs.
Hysteria: Although this indication is mentioned in the package insert, hysteria does not appear as a veterinary diagnosis in veterinary texts. As it is undefined in the package insert, it is unclear what exactly it refers to.


Patients with a history of seizures.
Animals exposed to organophosphates.
Animals that have been treated with Procaine hydrochloride.
Pre-existing severe central nervous system depression e.g. following large doses of barbiturates or opiates.

Idiosyncratic reactions to acepromazine in dogs

An Australian vet described in 1958 how he had premedicated a bitch presented for ovariectomy with chlorpromazine (also a phenothiazine). Forty-five minutes later, the otherwise friendly dog "had become extremely savage, biting me twice before I managed to control her" (Collard, 1958).

A Canadian veterinarian described in 1982 two similar cases involving acepromazine where dogs of pleasant temperament suddenly became extremely aggressive shortly after the administration of acepromazine. In the one case, which involved a terrier-type bitch, the veterinarian sustained 64 punctures and 11 lacerations on his hands. The other case was a Chihuahua which was premedicated for spaying and within 20 minutes of administration of the drug became very aggressive (Waechter,1982).

Meyer (1997) describes a few other cases where acepromazine administered for various reasons in otherwise tractable dogs, resulted in sudden, severe aggressive behaviour, both towards people and other dogs. In one case, another dog was killed by the dog treated with acepromazine.

Although this type of reaction is apparently uncommon, it is mentioned in veterinary pharmacology textbooks (Booth, 1988). No mention, however, is made in the current package insert of acepromazine products. Acepromazine is extremely widely used by veterinarians and considering the potentially serious consequences such a reaction could have, particularly if it involved children, it would be prudent for veterinarians to be aware of this possible reaction and act pro-actively.

Veterinarians are advised to caution clients about the possibility of such a response, particularly when the drug is dispensed for home use, or a patient still under the influence of acepromazine is discharged. Advising clients not to leave the treated dog unsupervised with children, disabled adults or other pets could prevent injury to people and dogs.

Considering the fact that several cases of aggression following administration of acepromazine have been documented in the literature, veterinarians could be held liable for injury caused by dogs treated with acepromazine if clients are not made aware of this possible effect.

Practical application of acepromazine for behavioural problems

Acepromazine is often prescribed by veterinarians for the treatment of behaviour problems, especially in dogs. It is most commonly used for sound phobias (i.e. dogs with phobic reactions to thunderstorms, fireworks, gunshots etc) and for problems involving aggression. It should be noted that these indications are not mentioned in the package insert.

1. Use of acepromazine in aggressive patients:

    1. Routine tranquillisation of aggressive patients

The possibility of rare idiosyncratic responses to acepromazine as described in otherwise non-aggressive dogs, is also possible in aggressive dogs, thereby increasing the intensity of agonistic behaviour in such cases. Acepromazine should therefore be used with care in aggressive patients.

    1. Treatment of inappropriate aggression

Aggression is the most common canine behaviour problem in veterinary behavioural medicine referral practices. This includes aggression to people as well as interdog aggression.

Acepromazine is inappropriate as a treatment for canine aggression. The main reason is its lack of specificity and its numerous side effects (Thompson, 1998). Acepromazine merely blunts (normal and abnormal) behaviour instead of addressing the underlying cause. It interferes with learning thereby reducing the effectiveness of behavioural modification programmes. The level of duration and tranquilisation also varies, making its effect unpredictable. Dogs under the influence of acepromazine are more reactive to noises and startle, and therefore more likely to react aggressively (Overall, 2001). Any perceived threat will increase the adrenergic tone, which in turn will reverse the hypotension caused by acepromazine providing sufficient strength to bite someone (Joubert, 2003).

The treatment of canine aggression is complex and each case must be assessed individually by a veterinarian with a solid understanding of animal behaviour, in order to provide the client with the best treatment options and an accurate prognosis. Where drug therapy is required, drugs with far more specific effects are available. Readers are referred to Overall (1997), Overall (2001) and Zulch (2002) for more information on this topic.

The handling of dogs that are aggressive in the specific context of a visit to the veterinary practice is covered by Joubert (2003) and Sonntag (2003).

  1. Treatment of sound phobias

Acepromazine is considered inappropriate treatment for sound phobic pets (Overall, 1997; Dodman,1998; Heath and Bowen, 2003). It produces marked tranquillisation and poor anxiolysis. As a result of its potent tranquillisation effect, it is often used to prevent self-trauma or property damage in sound (e,g. fireworks, thunderstorm) phobic dogs. However, acepromazine makes dogs more likely to startle and react to sounds. Therefore although it may prevent the problem behaviour (attempts at hiding or escaping) from occurring, it does nothing to address the underlying anxiety. It is likely to worsen the underlying phobia because it tends to sensitise the dog to the sound rather than desensitise it, hence the term chemical straightjacketing.

The recommended treatment for sound phobic pets is to address the acute manifestation of the phobia with appropriate anxiolytic drugs and to address the underlying phobia with a combination of behavioural management and longer term appropriate medication.

The drugs of choice for acute treatment of noise phobias are the longer acting benzodiazepines such as alprazolam (0,01-0,1 mg/kg for dogs and 0,125-0,25 mg/kg for cats as needed up to bid) and oxazepam (0,2-1 mg/kg for dogs and 0,2 to 0,5 mg/kg for cats as needed up to bid). These drugs are not registered for use in dogs and cats thus all the normal precautions of extra-label use must be observed.

Behavioural management and long term drug therapy will help many pets cope better with the underlying anxiety by becoming habituated to the sounds which produce the phobic response. This topic does not fall into the scope of this article, but readers are referred to Sonntag (2002) and Heath and Bowen (2003) for more information.


Acepromazine is a widely used drug that has specific indications in veterinary medicine. Rare idiosyncratic reactions do occur and have been documented. Veterinarians must be aware of this, and inform clients of such when using the drug in order to ensure that they are not held responsible for the consequences of such reactions.

Where acepromazine is used for "intractable" patients, this refers to patients who are hyperexcitable due to their exuberant temperament. Patients who are truly anxious or aggressive, would benefit from other pharmacologic agents (Joubert, 2003).

Specific anxiolytic drugs, in combination with behavioural management / modification protocols are indicated in some behavioural disorders. Veterinarians who are not familiar with these protocols and drugs should rather consult with or refer such cases to veterinary behaviour specialists or veterinarians with a particular interest in behavioural medicine.


Booth NH 1988 Psychotropic agents In: Booth NH and McDonald LE, ed. Veterinary Pharmacology and Therapeutics 6th ed. Iowa State University Press

Collard 1958 Unusual reaction to chlorpromazine hydrochloride in a bitch The Australian Veterinary Journal 34:90

Dodman NH 1998 Pharmacologic treatment of aggression in veterinary patients. In: Dodman NH and Shuster L, ed Psychopharmacology of animal behavior disorders Blackwell Sciences Inc

Heath SE and Bowen JE 2003 Canine sound phobias – a review of treatment approaches Proceeding no 352: 4th International Veterinary Behaviour Meeting p 237-244

Joubert KE 2003 The chemical restraint of vicious dogs Insert: Newsletter of South African Veterinary Council April 2003

Meyer EK 1997 Rare, idiosyncratic reaction to acepromazine in dogs Journal of the American Veterinary Medical Association 210:8 p 1114-1115

Overall KL 1997 Behavioral pharmacology. In: Overall KL Clinical Behavioral Medicine for Small Animals Mosby, St Louis, USA

Overall KL 2001 Pharmacological treatment in behavioral medicine: The importance of neurochemistry, molecular biology and mechanistic hypotheses The Veterinary Journal 162:9-23

Sonntag Q 2002 On Best Behaviour: Noise phobias VetMed 15:2 August 2002

Sonntag Q 2003 Dealing with aggressive canine patients: A behavioural perspective Insert: Newsletter of South African Veterinary Council No 32

Thompson 1998 Pharmacologic treatment of phobias. In: Dodman NH and Shuster L, ed Psychopharmacology of animal behavior disorders Blackwell Sciences Inc

Waechter RA 1982 Unusual reaction to acepromazine maleate in the dog Journal of the American Veterinary Medical Association 180:73-74

Zulch H Dominance aggression in dogs VetMed 15:2 August 2002

(Published -March 2004)

Correct dosage of alprazolam in cats

In the article "The use of acepromazine (ACP) for behavioural disorders in dogs and cats" (insert in Newsletter 36), the use of alprazolam as an anxiolytic for dogs and cats was mentioned and certain dosages given.

The dosage for dogs (0,01- 0,1 mg/kg) was obtained from the Proceedings of the 4th International Veterinary Behaviour Meeting held in Australia in 2003. As this reference did not provide a dosage for cats, the dosage for cats (0,125 –0,25 mg/kg) was taken from the textbook Clinical Behavioral Medicine for Small Animals (KL Overall, 1997).

However, in The Veterinary Journal 2001, 162, 9-23 in Pharmacological treatment in behavioural medicine: The importance of neurochemistry, molecular biology and mechanistic hypotheses, the author, KL Overall, states the following dosage for cats: 0,01 – 0,02 mg/kg per os every 12 hours.

As this discrepancy in dose rate is quite large it is recommended that the most recently published dose rate is used. Although the higher dosages have been used in cats with no apparent detrimental effect, practitioners are advised to use the lower dose rate of 0,01 – 0,02 mg/kg and titrate upwards to effect. The calming effect is usually evident before any motor incoordination is seen, thus a dosage that produces signs of motor incoordination is probably too high.

Dr Quixi Sonntag (BVSc)(Hons)

(Published Newsletter 38, November 2004)

Adverse Drug Reactions

Adverse drug reactions and side effects of drugs

Courtesy of Veterinary Surgeons' Board of WA-Newsletter March 2003

as adapted for SA circumstances by Prof G E Swan, Professor and Head Department of Paraclinical Sciences, University of Pretoria

The following information sheet (slightly adapted for S A circumstances) is given to clients of a particular clinic in Western Australia. What do you think?

"All drugs can have side effects or may present an adverse drug reaction. These are usually minor and are not experienced by all animals. Most will disappear when the treatment is stopped. The benefits of the medication usually far outweigh any risk associated with adverse drug reactions. If you have any concerns or worries that your animal may be reacting in any way please contact the hospital immediately so that they can be discussed.

Below are some of the more commonly used drugs and their possible adverse drug effects.


These are given annually to prevent diseases for which there is no specific treatment. Occasionally they can give rise to allergic reactions such as hives (skin swellings) and swollen faces. Some animals can become lethargic, have a transient fever and very rarely collapse. Also a local swelling may appear at the injection site. This usually resolves over 3-4 weeks.

ANTIBIOTICS (e.g. penicillin, amoxycillin, cephalexin, ceftiofur, gentamicin, oxytetracycline, doxycycline, clindamycin, tylosin)

These drugs are used to control bacterial infections. However antibiotics can affect a range of bacteria, good as well as bad, hence if given by mouth diarrhoea may occur. (Plain yogurt may help restore the normal gut flora) Some animals may also vomit with certain antibiotics.

WORM MEDICATIONS (e.g. albendazole, ivermectin, closantel, praziquantel, nitroscanate, pyrantel, piperazine)

These are used on a regular basis to control intestinal worms but occasionally cause the animal to vomit soon after dosing. If this happens within 2 hours re-deworming is necessary later.

NON STEROIDAL ANTI-INFLAMMATORIES (e.g. phenylbutazone, flunixin, meloxicam, carprofen)

They are used to control pain and inflammation. Cats are very sensitive to them and they should not be combined with each other or used along with cortisones. The most common effect, though less often seen these days, is gastrointestinal bleeding.

CORTISONE (e.g. hydrocortisone, prednisolone, dexamethazone, betamethathone, flumethazone, triamcinolone)

These are used for their anti-inflammatory and anti-allergic effects, and also to cause immunosuppression in certain conditions. The most common side effects are increases in appetite and thirst (and consequently increased urination). You may also see lethargy and panting. Do not restrict your animal's water intake but keep the food intake the same. These effects disappear as reducing dose regime continues. When the drugs need to be used long term in high doses they can result in liver disease, gastric ulcers, diabetes, pancreatitis, lack of oestrus, testicular atrophy, lack of libido, Cushing disease symptoms- hair loss, thick skin, reduced thyroid function, weakness, reduced exercise tolerance, slow wound healing, increased risk of infection and weight gain.

We taper the dose and alternate days to minimise these effects.

ANTIHISTAMINES (e.g. promethazine, diphenhydramine, chlorpheniramine, cyclizine)

These are commonly used to control allergic reactions. They may cause drowsiness. Long term use may occasionally cause loss of appetite, nausea, vomiting, constipation and diarrhoea.


These are generally very safe but some animals can react adversely, resulting in occasional deaths. Hence there is a risk with any anaesthetic, although very slight. We are extremely careful and offer a range of alternatives depending on likely susceptibility to age and illness (heart, liver and kidney problems for example)

Please discuss this with your vet if you have any concerns.

There are other drugs we use and obviously individual animals can show various reactions. Our vets will advise you of any likely problems but obviously many reactions are totally unexpected and have to be dealt with as and when they arise. Please let us know if you have any concerns with your pet's medications. "

Does your clinic/ hospital hand out similar information sheets? What do you think of handing out such information?

Veterinarians and clients should take note thereof that all suspected adverse drug reactions or events observed following the use of drugs in animals must be reported to the Pharmacovigilance Centre at the Faculty of Veterinary Science, University of Pretoria. A copy of the reporting form can be found in each copy of the IVS or can be requested from the centre at:

Veterinary Pharmacovigilance Centre

Department of Paraclinical Sciences

Faculty of Veterinary Science

University of Pretoria

Tel: (012) 529 8239

e-mail This email address is being protected from spambots. You need JavaScript enabled to view it.

The Pharmacovigilance Centre is the official centre of the Medicines Control Council for reporting of adverse drug reactions or events in animals but also receives and evaluates adverse reactions associated with the use of stock remedies. Drug failure or reduced efficacy is also classified as a suspected adverse drug event.

Animal Experimentation


Animal experimentation according to modern scientific principles has been going on for over a century.  The results in surgery, medicine, infectious diseases, pharmacology and other disciplines have been of enormous benefit to both animals and humans.  They have also had cumulative affects of accelerating knowledge in many directions as one discovery leads to another.

The SAVC believes that animal experimentation has and will continue to form the basis of much veterinary and medical knowledge.

With rare exceptions, mammalian anatomy and physiology share many more similarities than differences.  Responses in toxicity and efficacy trials are indeed reliable for screening products for possible use in humans and other animals.  The same principles apply to surgical and diagnostic procedures, including modern imaging techniques.

The relief of human and animal suffering and the saving of lives far outweigh the relatively small sacrifices in animal experiments.  As an example, many millions of humans and animals have been treated successfully for diabetes since the discovery of insulin by Best and Banting in 1921 and their experiments in animals.  In this example the hormone involved and the responses to it are remarkably similar between the species. The same has been true for countless other experiments.

New knowledge often has the surprising result of being applicable to humans or animals in unpredictable and unforeseen ways.  It may therefore be considered good in itself because of the options and possibilities it opens up.  Animal experimentation that is directed at solving human problems also benefits animals because of the knowledge gained in technique, materials and use of medicines.

For these reasons the SAVC believes it to be irrational for veterinarians to deny a very large part of their present and future foundation of knowledge.

It is aware of the possibility of abuse and subscribes to the principles of the National Code on Animal Experimentation.

Adherence to this code will result in: -

  1. No unnecessary or duplicated experiments;

  2. Protocols that ensure the use of minimum number of animals with minimal suffering and sacrifice;

  3. A transparency that ensures high quality ethical and scientific screening of proposals and monitoring of experiments as they are performed.

The SAVC also supports replacement of animal experimentation with alternative experimental technology whenever possible as well as refinement of animal experimental protocols to further limit suffering and sacrifice.

The SAVC is involved in initiatives to plan new legislation based on the National Code on Animal Experimentation which will include a regulating Council and institutional Animal Ethics Committees in all institutions which conduct experiments. Such committees will have mandatory involvement of veterinarians and animal welfare representatives.

(Published June 1997, courtesy of Dr P C Ardington)

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