Behaviour Modifying Drugs - Overview

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Although many drugs are used to treat behavioural conditions in animals, there are only three psychoactive drugs specifically licensed for use in companion animals to treat behavioural problems. These are:

  • Clomipramine (licensed in the dog for treatment of separation anxiety)
  • Selegiline (licensed in the dog for treatment of canine cognitive dysfunction syndrome)
  • Fluoxetine (licensed in the dog in the USA for treatment of separation anxiety)

Several other drugs are often used to treat behavioural conditions, such as propranolol, phenobarbitone, diazepam and various other common veterinary drugs, however, these are not licensed for this purpose. In addition many other drugs are used in behavioural medicine but most are unlicensed for use in any animal species. Examples are listed in the table below, however, most uses listed are unapproved, care should therefore be taken with their use:


Class of Drug Drugs Uses Side Effects
Tranquilizers Acepromazine Sedation/restraint Hypotension, CNS stimulation, contradictory responses. Caution in boxers and greyhounds
Benzodiazepines Alprazolam, Clonazepam, Clorazepate, Diazepam, Lorazepam, Oxazepam Anxiety, noise phobias, canine submissive urination, feline urine marking Sedation, ataxia, increased appetite, paradoxical excitation
Tricyclic Antidepressants (TCAs) Amitriptyline, Clomipramine, Doxepin, Imipramine Anxiety, separation anxiety, canine and feline fear aggression, feline urine marking, feline compulsive grooming, stereotypy, some narcoleptic disorders Sedation, gastrointestinal (GI) effects, dry mouth, increased thirst, urinary retention
Selective Serotonin Reuptake Inhibitors (SSRIs) Fluoxetine, Fluvoxamine, Paroxetine, Sertraline Aggression, canine separation anxiety, compulsive disorders, feline urine marking Lethargy, inappetence, anorexia, GI effects
Beta Blockers Propranolol Canine fear aggression, noise phobia Bradycardia, lethargy, hypotension, syncope
Azapirones Busiprone Phobia, anxiety, feline urine marking, interact aggression Uncommon, not sedating
Triazolopyridines Trazodone
Anticonvulsants Carbamazepine, Gabapentin, Levetiracetam, Phenobarbital, Potassium bromide Canine and feline compulsive tail chasing, unprovoked canine rage aggression Lethargy, ataxia, polyuria, polydipsia, polyphagia
Hormones Medroxyprogesterone acetate, Megestrol acetate Last resort for aggression and feline urine marking Polyphagia, polydipsia, sedation, diabete mellitus, pyometra, mammary hyperplasia, endometrial hyperplasia, carcinoma
Glial Modulators Propentofylline
Monoamine Oxidase Inhibitors (MAO-Is) Selegiline Canine and feline cognitive dysfunction syndrome, fear related problems, spraying, hyperactivity, compulsive/stereoptypical disorders, specific phobias GI effects, restlessness or lethargy, anorexia


Benzodiazepines are the only class of drug that consistently succeeds in all models, but this may be why they have a dangerous disinhibitory effect on aggression. These drugs eliminate avoidant responses to many kinds of aversive events, increasing confidence in a number of exploratory tests. This is why benzodiazepines can cause dangerous levels of disinhibition in aggressive dogs. Benzodiazepines also inhibit memory formation by affecting NMDA (glutamate) receptors in the hippocampus, which limits their usefulness in behavioural therapy where any kind of learning is required, which is in most situations. They are useful for memory blocking if given at sub-sedative doses prior to or during a predicted traumatic event such as a thunderstorm. When used at low doses, they act as mild tranquillisers, this can help moderate excitement. At medium doses they lessen anxiety, which can encourage social interaction in a constructive way [1].

Drugs such as Acepromazine (ACP), which act on dopamine receptors, and synthetic hormone analogues like megestrol acetate (Ovarid), have little or no rational use in behavioural therapy for reasons of non-specificity, and adverse effects which make their use unjustifiable.

Phenothiazines such as ACP have a very varied level of effect and duration of action and dull both normal and abnormal behaviours which is an out of date approach to behavioural therapy[1].

The first port of call when using medication for behavioural problems should be drugs licensed for veterinary use. These drugs have established data about their efficacy, side effects, contraindications and toxicity, which makes expected outcomes more reliable[2].

References

  1. 1.0 1.1 Overall, K.L., 2004. Paradigms for pharmacologic use as a treatment component in feline behavioral medicine. Journal of Feline Medicine and Surgery 6, 29-42.
  2. Merck Veterinary Manual (10th Edition) - Behaviour. 2011 The Merck Publishing Group.