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Amitriptyline is a tricyclic antidepressant developed in 1960 to treat behavioral and mental illnesses in humans. In recent years, amitriptyline has found its way into veterinary medicine as an off-label treatment for anxiety, depression, excessive grooming, compulsive behaviors, and self-harm in canines and felines.

Tricyclic antidepressants boost serotonin and norepinephrine — the neurotransmitters responsible for making us feel "happy". Certain antidepressants, like amitriptyline, also have anticholinergic properties, meaning they prevent acetylcholine (a type of neurotransmitter) from binding to neuroreceptors. Many scientists believe neurochemical imbalances are responsible for mood disorders, and stabilizing levels can resolve the side effects of these conditions.

Dosage

A typical dose of amitriptyline is 0.5 to 2 mg per pound once or twice a day.

Dosage instructions

Your vet may recommend cutting amitriptyline tablets in halves or forths since it only comes in 3 strengths: 10 mg, 25 mg, and 50 mg. Amitriptyline may be given before or after meals since food doesn't inhibit its absorption. Keep in mind some antidepressants cause nausea when taken on an empty stomach. If your dog refuses to take medicine or seems nauseous after taking amitriptyline, try wrapping the tablet in a piece of meat or cheese.

Efficacy

There’s conflicting data regarding amitriptyline's efficacy as a treatment option for mood and behavioral disorders.

One randomized, independently-reviewed study on amitriptyline as a treatment for humans with clinical depression found that it was  more effective than the placebo at controlling symptoms of depression.

On the other hand, a separate clinical study of amitrtpyline for aggressive canines found there was "no significant difference" in temperament when using this medication for behavioral modification.

Side effects

  • Fatigue

  • Increased thirst

  • Constipation

  • Lightheadedness

  • Weight gain

  • Difficulties urinating

  • Excitability

  • Tremors

  • Change in heart rhythm

  • Low white blood cell counts

  • Agitation

  • Confusion 

  • Change in tongue color

Considerations

It takes most antidepressants 2 to 6 weeks to make a noticeable difference in mood. During this time, the body adjusts to the medicine and the change in brain chemistry.

This medication is not recommended for canines with epilepsy, since amitriptyline may trigger seizures in some dogs. Amitriptyline may exacerbate thyroid problems, heart arrhythmias, and some eye conditions. 

This medication may raise blood sugar levels in some dogs. Canines with type 1 diabetes should have their glucose levels closely monitored while on this medication. 

Studies show humans with liver disease are at a slightly higher risk for hepatotoxicity while on amitryptiline. Only use this medication in dogs with low liver function if the benefits far outweigh the risks. 

Refrain from using flea collars on pets taking this medication. Many of these collars contain MAOIs that can interact with amitriptyline. 

The FDA cautions against using this medication while pregnant or nursing since it's known to cause congenital defects in humans. It’s also not recommended for pregnant or lactating dogs. Amitryptiline may worsen adrenal gland tumors; canines with this condition should only take this medicine if absolutely necessary. 

Drug interactions

Extreme caution should be used when using amitriptyline for dogs in combination with any of the following medications:

  • Monoamine oxidase inhibitors (MAOIs)

  • Flea collars

  • Anti-thyroid drugs

  • Cimetidine

  • Anti-platelet medication

  • Non-steroidal anti-inflammatory drugs (like ibuprofen and aspirin)

  • Warfarin

  • Anticholinergic medications

  • Clonidine

  • Guanabenz 

  • Cardiac stimulants like arbutamine

  • Certain types of antidepressants

Allergic reactions and sensitivity

Do not use this medication if your pet has had reactions to tricyclic antidepressants in the past. Contact your vet immediately if your dog exhibits hives, swelling, or trouble breathing after ingesting this medication.

Frequently asked questions

My dog has been on amitriptyline for 3 weeks, and there aren't any changes in their behavior. Is it working?

All antidepressants take weeks and even months to regulate in the system. Just because you don't see any noticeable changes doesn't mean it's not working. It may take another few weeks before your dog's symptoms start to improve.

What should I do if I miss a dose of amitriptyline for dogs?

If it's been more than two hours since your dog's missed dose, wait until the next time their medication is due and continue their schedule as usual. Never double up on this medicine to make up for a missed pill. 

Is it normal for dogs to be very tired when they take amitriptyline? 

Drowsiness is a typical side effect of amitriptyline for dogs. Generally, the fatigue subsides after the dog adjusts to this medication after a few weeks. 

My dog cries continuously when I'm away. Is amitriptyline good for dogs with separation anxiety?

Separation anxiety is one of the most common reasons vets prescribe this medication to their patients. Many pet parents find amitriptyline significantly reduces their pet’s anxiety and improves overall wellbeing.

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Amitriptyline Questions and Advice from Veterinary Professionals

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