Retrospective study on the use of fluvoxamine in dog behavior pathologies.

Dr Joël Dehasse, Brussels (Belgium) (

Lecture given at the AVSAB meeting, New-Orleans, July 12, 1999
 © Dr Joel Dehasse, 1999 - www.joeldehasse


I have used fluvoxamine (FloxyfralR, LuvoxR), a SSRI medication, in dog productive behavior disorders (disorders generating behaviors and nuisances, and lack of inhibitory signs).    



The behavioral signs (symptoms and disorders) of 37 dogs from my own practice (mono-centric study) have been retrospectively analyzed using an identical questionnaire and evaluation sheet. The required criteria were that the dog had to receive fluvoxamine only (without any other interfering medication) and that there had to be at least one control evaluation (after one month).

The 37 dogs were divided in 19 (51%) females (9 spayed) and 18 (49%) (5 castrated) males. The reported age was at an average of 2,2±1,5 years old, with a minimum of 3 months and a maximum of 5,5 years.

Fluvoxamine was given at the dose of 0,5 to 2 mg twice a day on the basis of response and tolerance (individual adaptation of the highest dosage giving response, without signs of sedation).

To analyze the data, I decided that to be significant, I had to observe at least an improvement of 50% of the dogs (with a Khi2 test; p=0,05). It means that I will accept that 50% of the dogs may improve independently of the drug. I did not use a placebo for ethical reasons (referred cases). This 50% value is higher than the average placebo effect. In a study reported in RxList (97), fluvoxamine was tested against placebo in two 10-week multicenter, parallel group studies of adult outpatients with OCD; improvement due to fluvoxamine was recorded at 65% against 44% for placebo.

  When a behavior therapy was prescribed, it had to begin after one month of the drug treatment.

  The examination of the data shows that several disorders have improved during the first month (the 37 dogs totaled 47 diagnosed disorders):

  • From 45 productive disorders, including hierarchy disorders with dominance aggression, including also hallucinations, general anxiety, phobia and overactivity disorder: 37 improved (82%), 8 unchanged (Khi2=18, p<0,005).

  • From 16 overactive and/or hyperactive disorders: 14 improved (88%), 2 unchanged (Khi2=9, p<0,005)

  • From 18 phobic or anxious disorders: 14 improved (78%), 4 unchanged (Khi2=5,5, p<0,025).

  The examination of the data shows that several symptoms have significantly improved (the 37 dogs totaled 271 recorded symptoms at day zero):

  • Waking at night and hyposomnia: 13 improved (81%), 3 unchanged during the first month (Khi2=6,25, p<0,025). This effect was confirmed after 2 months of treatment: 9 improved, 1 unchanged (Khi2=6,4, p<0,025).

  • All aggressive behaviors in general (sum of the different aggressive behaviors including defense aggression): 26 improved (45%), 31 unchanged after the first month (not significant). This is significant only after the second month of treatment: 20 improved (71%), 8 unchanged (Khi2=5,1, p<0,025).

  • Aggressive behaviors excluding defense aggression (territorial, irritation and fear aggressions): after 2 months of treatment: 13 improved, 4 unchanged (Khi2=4,8, p<0,05).


Other symptoms were improved, but they were not seen at a frequency high enough to do a statistical analysis: bulimia (27%, 11 cases), polydipsia (57%, 7 cases), destructiveness when alone (75%, 4 cases), hypervigilance (38%, 21 cases), lack of psycho-motor control (75%, 8 cases), emotional digestive symptoms (100%, 2 cases), etc.

Fluvoxamine has shown very little or no significant modification of normal behaviors (1,25% on 80 symptoms): appetite, thirst, self-licking, sleep, scanning, elimination, obedience, attachment and sexuality. This was recorded as well after one month of treatment as for longer treatments of about 5 to 6 months.


The side effects related to the treatment were:

  • short term sedation (subjective estimation around a quarter of the cases, leading to an obligation to increase the therapeutic dosage progressively) or long term sedation (2,7%). hyporexia (8%) or bulimia (5,4%)  

  • reduced psycho-motor control (5,4%)

No compliance difficulty was reported.  



As a SSRI drug, fluvoxamine maleate acts on the 5HT1A receptor. The 5HT1 receptor seems to inhibit or at least regulate the dopamine, noradrenaline and acetylcholine neurotransmissions (Meunier, Shvaloff, 1995). In vitro studies do not show any direct affinity for the histamine, noradrenaline, muscarine or dopamine receptors (RxList, 97).

Serotonine is a precursor of melatonin in the pineal gland and in the suprachiasmatic nucleus, two structures arbitrating the biological clock. Melatonin induces sleep. This model may explain how SSRI may induce sleep without having antihistaminic properties (Meunier & Schvaloff, 1995). This may also explain the high percentage of significant effectiveness of fluvoxamine on hyposomnia and insomnia.

In people, fluvoxamine has nonlinear pharmacokinetics over the range of 100 to 300 mg/day. “Higher doses produced disproportionately higher concentrations than predicted from the lower dose” (RxList, 97).

The increase of the dose is advised in human medicine from 50 mg once at bedtime to 200-300 mg/day in 4 to 7 days (RxList, 97). I encountered the same sedative difficulty at the beginning of treatment and had to increase the dose progressively over a period of one week.

Fluvoxamine seems to be a regulator of the behavior sequence, reintroducing - where it is absent - the introductory (beginning) and ending phases and decreasing the intensity of the operant (the attack) phase. This may help to reduce overactivity and aggression.  



Fluvoxamine is a potent anti-impulsiveness, anti-overactivity, anti-aggression medication at a dosage varying between 0,5 to 2 mg per kilo twice a day.  



  • Meunier J.-M., Shvaloff A. Neurotransmetteurs. Masson, Paris 1995.

  • Hamon M. Sérotonine, in Epelbaum: Neuropeptides et neuromédiateurs, Les éditions INSERM, Paris, 1995.

  • RxList Generic Information. 28 February 97.  

    Dr Joël Dehasse - Behaviorist veterinarian