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Effect of High Doses of Fluoxetine in Hyperactive Dogs

Meghan E. Herron, DVM, DACVB, Gigi’s Shelter for Dogs, Canal Winchester, Ohio

Behavior

|
March 2022

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In the literature

Bleuer-Elsner S, Muller G, Beata C, Zamansky A, Marlois N. Effect of fluoxetine at a dosage of 2-4 mg/kg daily in dogs exhibiting hypersensitivity-hyperactivity syndrome, a retrospective study. J Vet Behav. 2021;44:25-31.


FROM THE PAGE …

Fluoxetine (1-2 mg/kg PO every 24 hours) is FDA-approved for treatment of separation anxiety in dogs; doses >2 mg/kg PO every 24 hours are uncommon, likely due to concern for adverse effects at higher doses and lack of supportive published evidence. 

This study describes extra-label use of fluoxetine to treat hypersensitivity-hyperactivity (HSHA) syndrome, which is characterized by hypermotricity (eg, compulsive exploration of a room, difficulty lying down and resting), difficulty sleeping, and lack of satiety.1 Clinical signs of HSHA are similar to attention-deficit/hyperactivity disorder in humans. 

This study includes the first published data on treatment of HSHA with fluoxetine and is the first to suggest that doses of 2 to 4 mg/kg PO every 24 hours can be well tolerated. Although 88 out of 89 dogs showed improvement in clinical signs, ≈46.1% also experienced adverse effects (ie, lack of appetite, fatigability, sedation, tremors, weight loss), and 10.1% were highly or severely affected. Decreased appetite was significantly correlated with satiety improvement, suggesting lack of appetite might have been considered a positive effect. 

This study was limited by its retrospective nature, as true efficacy compared with placebo (as might be demonstrated in a randomized, double-blinded, placebo-controlled study) could not be confirmed; however, it brings attention to a syndrome not often described in the United States and encourages reconsideration of the traditional fluoxetine dose (ie, 1-2 mg/kg PO every 24 hours). 


… TO YOUR PATIENTS

Key pearls to put into practice:

1

In the absence of physical disease, diagnosis of HSHA syndrome should be considered in dogs presented with hyperactive behaviors, interrupted sleep patterns, and insatiable appetites.

2

Fluoxetine administered above the traditional dose may be considered, but pet owners should understand this is extra-label and adverse effects are possible. Monitoring for adverse effects and subsequently adjusting the dose are key to maximizing the benefits of the higher dose range.

3

In dogs with HSHA syndrome currently receiving and tolerating fluoxetine at <2 mg/kg PO every 24 hours, increasing to 2 to 4 mg/kg PO every 24 hours may result in greater clinical improvement.

 

4

Decreased appetite may be a beneficial response in dogs that lack satiety control and should be considered when selecting selective serotonin reuptake inhibitors.

References

For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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