Amitriptyline HCl

What is this medication for?

• Behavior disorders (anxiety), adjunct for itching, neuropathic pain
• Chronic idiopathic cystitis (long-term only), itching adjunct, neuropathic pain

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.

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

• Sedation, anticholinergic effects (dry mouth, urinary retention, constipation) (Most predominant)
• Reduced grooming, weight gain, drowsiness (Common)

Worth a phone call to your veterinarian

• Cardiac dysrhythmias, bone marrow suppression (rare, high dose) (Rare)

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

• Hyperexcitability, rarely seizures (Uncommon)

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

• has or has had: Prior TCA hypersensitivity; concurrent MAO inhibitors (selegiline, amitraz)
• has or has had: Seizure disorders (may ↓threshold), thyroid disease, hepatic disease, dry eye, glaucoma, cardiac rhythm disorders, diabetes, adrenal tumors — use with caution

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • MAO inhibitors (selegiline, amitraz)
  • SSRIs (fluoxetine)
  • Cimetidine
  • Cisapride, quinidine
  • Sympathomimetics

Storage and handling

Room temperature, tight container, protect from light. Injectable form no longer marketed in the US.

Good to know

• Bitter-tasting tablet, notoriously difficult to dose orally in cats — discuss compounding options with owners upfront.
• For idiopathic feline cystitis, short-course treatment (≤7–10 days) has been shown ineffective in controlled trials — only consider for chronic/recurrent disease under close supervision, not acute flares.
• Generally considered less effective than clomipramine for canine compulsive disorders and did not outperform placebo for aggression in controlled study — set realistic expectations.