Paroxetine HCl

What is this medication for?

• Aggression, stereotypic/compulsive behaviors; generalized anxiety; phobias/fears (adjunct)
• Occasional use for anxiety/behavioral disorders

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• Paxil's personality: the most potent, most anticholinergic, most interaction-prone SSRI — and the one with the worst human discontinuation syndrome → always taper.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Anorexia, low energy/tiredness, stomach/intestinal effects, anxiety, irritability, insomnia/hyperactivity, panting (Profile not fully established)
• Aggression in previously unaggressive dogs (Possible)
• Behavior changes, loss of appetite, constipation, elimination-pattern changes (Feline profile)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Hypersensitivity; MAO inhibitor co-therapy (selegiline, amitraz)
• has or has had: Severe cardiac/renal/hepatic disease (reduce dose); seizure history (class); bleeding risk (platelet serotonin effect)

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • MAOIs (selegiline, amitraz)
  • Tramadol, trazodone, other serotonergics
  • CYP2D6 substrates
  • NSAIDs/anticoagulants

Storage and handling

Room temperature; tablets/suspension.

Good to know

• Paxil's personality: the most potent, most anticholinergic, most interaction-prone SSRI — and the one with the worst human discontinuation syndrome → always taper.
• The "aggressive behavior in previously unaggressive dogs" line appears across the SSRI files — owner-warned monitoring matters in aggression cases specifically.
• Perrin: constipation in cats is the paroxetine-specific feline note (vs fluoxetine's appetite suppression).