Drugs and Behaviour: What, When and Why?
World Small Animal Veterinary Association World Congress Proceedings, 2007
Diane Frank, DMV, DACVB
Université de Montréal, Faculté de Médecine Vétérinaire, Centre Hospitalier Universitaire Vétérinaire
St-Hyacinthe, QC, Canada

Which patients should we medicate and for how long? Drugs in behavioural medicine are generally prescribed to decrease anxiety or reactivity, thus facilitating implementation of behaviour modification techniques and in some cases accelerating rate of progress. Antidepressants can help achieve these goals if patients are carefully selected.


Anxiety in humans is defined as the anticipation of a future danger or threat, real or imaginary. Anxiety can be normal or a sign of an illness. This definition can also be used for animals. Most dogs and cats presented to the veterinarian are fearful or anxious. Some will remain anxious as long as they are on the table but are fine when they are back on the floor or out the door from the veterinary hospital. These patients are normal. On the other hand, separation anxiety, panic disorder, generalized anxiety, phobias and obsessive-compulsive disorders are sub-groups of anxiety disorders.

Behaviours and Body Language During the Appointment

During a behavioural consultation, the animal is usually free to move around the room. Physical examination is done at the end of the appointment. Dogs can express anxiety (and/or fear) by panting, puffing their cheeks, crinkling their brow, yawning repeatedly, licking their lips constantly, pulling their ears backs, trembling, tucking their tail, trying to back up or escape, hiding, whining, or even seeking owner attention excessively. Many anxious dogs will have dilated pupils, will pace, and are unable to settle down and relax. Each sign is non-specific. Anxiety (or fear) can result in urination, defecation or excessive salivation. Finally aggression may also be a sign of anxiety. Similarly cats can express anxiety (and/or fear) by panting, licking their lips frequently, pulling their ears down and back, arching their back, tucking their tail, trying to escape, vocalizing, pacing, freezing or being aggressive. Each sign is non-specific.

Some animals will have increased motor activity whereas others will have decreased motor activity. Vigilance may be increased. Reactivity during the appointment may be exaggerated and may even increase over time. Exploratory behaviour of the consultation room may be absent and should be distinguished from increased motor activity. These behaviours serve as baseline and can be compared with behaviours expressed during follow-up visits.

Anxiety during the behavioural consultation is not sufficient to conclude that a given animal suffers from an anxiety disorder. But clients during the appointment are educated on how to recognize subtle signs of their animal's anxiety or fear. Following the appointment they will be much more attentive to the animal's body language and behaviours. They may realize that their animal is exhibiting signs of anxiety on a daily basis in the home environment in the absence of an identifiable cause. In the latter case, their animal is perhaps suffering from an anxiety-related disorder. The veterinarian should make it a point to ask if signs of anxiety (or fear) occur when the dog or cat is in its familiar environment and determine if that anxiety/fear is appropriate for the context.


Excessive reactivity can also be an indication of illness. An animal becoming more and more aggressive during the appointment in the absence of any threat may be "over-reactive". An animal becoming disobedient may in fact be "over-reactive" in that context. This animal is unable to hear ("emergency mode") any commands. Ask a person if following a near miss car accident, he/she would be able to tell what song had just played on the radio at the time of that close call... The ears may have heard the song but the brain did not register the information, as it was not essential for survival... Dogs and cats in "emergency mode" will require medication to decrease the level of reactivity.


Objective baseline data are obtained from tapes. Videotapes of the animal at home may reveal signs compatible with anxiety and in some cases may even be indicative of generalized anxiety. Videotapes are essential to confirm diagnosis of separation anxiety as well as assess response to pharmacological treatment. Tapes are also very useful to identify occurrence of silent threats occurring between household pets (inter-cat or inter-dog aggression) that are often unrecognized or missed by clients.

Indications for Antidepressant Medication

1.  Signs compatible with generalized anxiety in familiar environments in the absence of danger or threat

2.  Reactivity during the appointment for behavioural evaluation increases over time without any threat to the animal

3.  Excessive reactivity to benign stimuli

4.  Behaviour sequence is altered (other medical conditions ruled out)

5.  Behaviour is inappropriate for the context

6.  Frequency, severity or duration of the behaviour is excessive for the context

7.  Recovery time after an undesirable behaviour is excessive

8.  Animal is in "emergency mode" during episodes of undesirable behaviour

Examples of the following criteria will be given with clinical cases and video presentations.

Setting Up Realistic Expectations and Follow-Up

It is very important to distinguish between client request or demand ("fix my dog") and client expectations (time frame for improvement, amount of improvement necessary to preserve the animal-human bond, realistic expectations, etc.). It is equally important for the veterinarian to have a clear idea in terms of observable behaviour changes expected with a given psychotropic medication so that he/she can educate the owner on what to look for. Initial goal of the medication may be solely to reduce reactivity so that the dog or cat can hear the client giving instructions. If an animal stays reactive for a long time following the initial trigger (for example a thunderstorm phobic dog still shaking two hours after the end of the storm), the first goal may be to decrease duration of recovery time. Then, the next step may be to reduce frequency and duration for some of undesirable behaviours such as pacing or whining. By taking care to collect accurate baseline values (frequency, duration, presence of mental illness, "emergency mode", progression over time, etc.) it becomes possible to 1) set realistic expectations for the role of antidepressant medication in the treatment plan and 2) objectively assess whether a given drug has the desired clinical effects for the patient.

Drug Classes and Dosages for Dogs: A Few Examples

Anxiolytics: Only Benzodiazepines Will be Discussed

 Diazepam: 0.5-2.2.mg/kg PRN (half life less than 1h so suitable for short-term use)

 Clorazepate: 2 mg/kg q12h

 Alprazolam: 0.02-0.1mg/kg q8-12h (0.02 mg/kg if given with clomipramine)


 Clomipramine (TCA): 1-3 mg/kg q12h

 Fluoxetine (SSRI): 0.5-1mg/kg q 24h

Drug Classes and Dosages for Cats: A Few Examples


 Clomipramine (TCA): 0.25-0.5mg/kg q24h

 Fluoxetine (SSRI): 0.5-1mg/kg q 24h


Behaviour consultations should be handled like any other request for professional advice. First the veterinarian must determine if the behaviour changes are within normal limits or whether these changes are compatible with illness. Differential diagnosis should include the possibility of "mental illness" if clinical signs are compatible. When mental illness is identified, pharmacological treatment can accelerate treatment response and in some cases is actually essential to initiate improvement.


1.  Casey Rachel, 2002. Fear and stress. In: BSAVA Manual of Canine and Feline Behavioural Medicine, Gloucester, UK.

2.  Center SA, Elston TH, Rowland PH, Rosen D, Reitz BL, Brunt IE, Rodan I, House J, Banks S, Lynch L, Dring L, Levy J. (1996): Fulminant hepatic failure associated with oral administration of diazepam in 11 cats. J Am Vet Med Assoc, Vol. 209 : 618-624

3.  Ciribassi J, Luescher A, Paloske KS, Robertson-Plouch C, Zimmerman A, Kaloostian-Whittymore L, (2003). Comparative bioavailability of fluoxetine after transdermal and oral administration to healthy cats. Am. J. Vet Res, Vol. 64 (8): 994-998.

4.  Dodman NH, Donnelly R, Shuster L, Mertens P, Rand W, Miczek K, (1996): Use of fluoxetine to treat dominance aggression. J Am Vet Med Assoc, Vol. 209: 1585-1587.

5.  Hart BL, Cliff KD, Tynes VV, Bergman L, (2005). Control of urine marking by use of long-term treatment with fluoxetine or clomipramine in cats, J Am Vet Med Assoc, Vol. 226 (3): 378-382.

6.  Hewson CJ, Luescher UA, Parent JM, Ball RO, (2000): Effect of clomipramine on monoamine metabolites in the cerebrospinal fluid of behaviourally normal dogs. Can J Vet Res, Vol. 64: 123-129.

7.  Hewson CJ, Conlon PD, Luescher UA, Ball RO, (1998): The pharmacokinetics of clomipramine and desmethylclomipramine in dogs: parameter estimates following a single dose and 28 consecutive daily oral doses of clomipramine. J. vet. Pharmacol. Therap., Vol. 21: 214-222.

8.  Hughes D, Moreau RE, Overall KL, Van Winkle TJ, (1996): Acute hepatic necrosis and liver failure associated with benzodiazepine therapy in six cats, 1986-1995. J. Vet. Emerg. Crit. Care: Vol. 6, No 1: 13-20.

9.  King JN, Steffan J, Heath SE, Simpson BS, Crowell-Davis SL, Harrington LJ, Weiss AB, Seewald W, CLOFUS Study Group, (2004). Determination of the dosage of clomipramine for the treatment of urine spraying in cats. J Am Vet Med Assoc, Vol. 225 (6): 881-887.

10. King JN, Maurer MP, Hotz RP, Fisch RD, (2000): Pharmacokinetics of clomipramine in dogs following single dose intravenous and oral administration. Am. J. Vet Res, Vol. 61: 74-79.

11. King JN, Maurer MP, Altmann BO, Strehlau GA, (2000): Pharmacokinetics of clomipramine in dogs following single dose and repeated-dose oral administration. Am. J. Vet Res, Vol. 61: 80-85.

12. Landsberg GM, Wilson Al, (2005). Effects of clomipramine on cats presented for urine marking. J Am Animal Hospital Association, Vol. 41 (1): 3-11

13. Landsberg GM, (2001): Clomipramine-Beyond Separation Anxiety. J Am Animal Hospital Association, Vol. 37: 313-318.

14. Landsberg G., Hunthausen W., Ackerman L., 2003. Handbook of Behavior Problems of the Dog and Cat. London, Saunders.

15. Litster AL, (2000): Use of Clomipramine for Treatment of Behavioural Disorders in 14 cats-Efficacy and Side-Effects. Aust. Vet Practit., Vol. 30 (2): 50-53.

16. Mertens PA, Torres S, Jensen C, (2006). The effects of clomipramine hydrochloride in cats with psychogenic alopecia: a prospective study. J Am Animal Hospital Association, Vol. 42 (5): 336-343.

17. Neilson JC, 2002. Fear of places or things. In: BSAVA Manual of Canine and Feline Behavioural Medicine, Gloucester, UK.

18. Overall KL, 2002. Noise phobias in dogs. In: BSAVA Manual of Canine and Feline Behavioural Medicine, Gloucester, UK.

19. Overall KL, 1997. Fears, Anxieties, and Stereotypies. In: Clinical Behavioral Medicine for Small Animals. St. Louis, Mosby-Year Book Inc., 209-250.

20. Overall KL, 1997. Protocols for behaviour modification. In: Clinical Behavioral Medicine for Small Animals. St. Louis, Mosby-Year Book Inc.

21. Pfeiffer E, Guy N, Cribb A, (1999). Clomipramine-induced urinary retention in a cat. Can Vet J., Vol. 40 (4): 265-267.

22. Pouchelon JL, Martel E, Champeroux P, Richard S, King JN, (2000): Effects of clomipramine hydrochloride on heart rate and rhythm in healthy dogs. Am. J. Vet Res, Vol. 61 No 8, 960-964.

23. Pryor PA, Hart BL, Cliff KD, Bain MJ, (2001): Effects of a selective serotonin reuptake inhibitor on urine-spraying behavior in cats. J Am Vet Med Assoc, Vol. 219, No 11: 1557-1561.

24. Reich MR, Ohad DG, Overall KL, Dunham AE, (2000): Electrocardiographic assessment of antianxiety medication in dogs. J Am Vet Med Assoc, Vol. 216: 1571-1575.

25. Seksel K, Lindemans MJ, (2001): Use of clomipramine in the treatment of obsessive-compulsive disorder, separation anxiety and noise phobia in dogs: a preliminary, clinical study. Aust Vet J., Vol. 79 (4): 252-256.

26. Seksel K, Lindemans MJ, (1998): Use of clomipramine in the treatment of anxiety-related and obsessive-compulsive disorders in cats: Aust Vet J., Vol. 76: 317-321.

27. Simpson BS, Papich MG, 2003. Pharmacologic management in veterinary behavioural medicine. In: Veterinary Clinics of North America, Small Animals; vol. 33, 365-404.

Speaker Information
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Diane Frank, DMV, DACVB
University of Montreal
QC, Canada

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