By Rania Gollakner, BS, DVM, MPH

What is paroxetine?

Paroxetine (brand names: Paxil®, Brisdelle®) is a selective serotonin reuptake inhibitor (SSRI) antidepressant used to treat canine aggression, anxiety, and stereotypic/obsessive-compulsive behaviors. In cats, it has been used to treat aggression, urine marking, and other behavior problems.  

Its use in cats, dogs, or birds to treat behavioral disorders is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is paroxetine given?

Paroxetine is given by mouth in the form of a tablet, capsule, or liquid suspension. It may be given with or without food; however, if vomiting occurs when dosed on an empty stomach, give future doses with food. If your pet’s appetite is decreased, try hand-feeding favorite foods. Measure liquid forms carefully. Do not give this medication with aged cheeses. Do not stop giving this medication abruptly after long-term use or withdrawal can occur.

This medication can take a few weeks before full effects are noted, but gradual improvements are usually appreciable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effects are sleepiness and decreased appetite. Other side effects include drooling, vomiting, diarrhea, constipation, difficulty urinating, muscle twitches, restlessness, sleeplessness, panting, dry/itchy skin, or vocalization. Serious side effects include seizures, aggressive behavior, hyperexcitability, or persistent lack of appetite.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Paroxetine should not be used in pets that are allergic to it or other SSRIs, or pets currently taking monoamine oxidase inhibitors (MAOIs). Use paroxetine cautiously in pets with aggression, seizures, diabetes, or severe heart, liver, or kidney disease. Use cautiously in pregnant, nursing, old, or sick pets. Do not stop this medication abruptly after long-term use or withdrawal can occur.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with paroxetine: alprazolam, beta-adrenergic blocking agents, buspirone, cyproheptadine, diazepam, diuretics, insulin, isoniazid, linezolid, MAOIs (includes some flea/tick collars), methylene blue, metoclopramide, mexiletine, moxifloxacin, nonsteroidal anti-inflammatory drugs, pentazocine, phenytoin, St. John’s wort, tramadol, trazodone, tricyclic antidepressants, or warfarin.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store paroxetine?

Store this medication at room temperature between 59°F and 86°F (15°C and 30°C). The liquid suspension should be stored below 77°F (25°C). Protect from direct sunlight.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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