Amitriptyline: Dosage, Uses, and Side Effects

Amitriptyline for Dogs, Cats, and Birds: Dosage, Uses, and Side Effects Guide

Overview

• Amitriptyline has an anti-depressive activity by blocking noradrenaline and serotonin reuptake in the brain.
• Also stabilizes mast cells so can reduce the impact on inflammatory irritation.

Uses of Amitriptyline

• Dogs:
  • Management of separation anxiety, compulsive disorders, and generalized anxiety.
  • Adjunctive therapy for neuropathic pain and refractory pruritus.
• Cats:
  • Treatment of psychogenic alopecia, idiopathic cystitis, and hypervocalization.
  • Reduces anxiety-related behaviors like inappropriate grooming or urination.
• Birds:
  • Adjunctive treatment for feather-plucking disorders and stress-related behaviors.

Dose of Amitriptyline 

Dose of Amitriptyline In Dogs:

• Initial dose: 1–2 mg/kg p.o. q12–24h.
• Dosage may be increased gradually based on clinical response, up to a maximum of 4 mg/kg p.o. q12h in chronic conditions.
• For chronic pain: Start at 1 mg/kg and adjust as needed for symptom relief.

Dose of Amitriptyline In Cats:

• Initial dose: 0.5–1 mg/kg p.o. q24h.
• For idiopathic cystitis: Start with 2.5–12.5 mg/cat p.o. once daily at night.
• Adjust frequency or dose (up to 1.5 mg/kg) based on response and tolerance.

Dose of Amitriptyline In Birds:

• Feather plucking: 1–2 mg/kg p.o. q12–24h.
• Higher doses (up to 9 mg/kg) may be required for severe cases; monitor closely for adverse effects.

Side Effects of Amitriptyline 

• Common side effects:
  • Sedation, dry mouth, vomiting, and constipation.
  • Hypotension, arrhythmias, and syncope.
  • Increased appetite and weight gain.
  • Ptyalism (drooling) in cats due to its bitter taste.
• Less common side effects:
  • Hyperactivity or excitability, seizures, and urinary retention.
  • Liver enzyme elevations, ataxia, or disorientation.
• Birds:
  • Dystonia, akathisia, or sedation at higher doses.

Contraindications of Amitriptyline

Avoid use in:

• Animals with:
  • Hypersensitivity to tricyclic antidepressants.
  • Glaucoma, urinary retention, or a history of seizures.
  • Severe liver disease or cardiac conduction abnormalities.
• Animals receiving monoamine oxidase inhibitors (e.g., amitraz, selegiline) or serotonin reuptake inhibitors (e.g., fluoxetine, clomipramine).

Some Notes:

• Drug Interactions:
  • Serotonin Syndrome Risk: Avoid combining with SSRIs (e.g., fluoxetine), MAOIs, or tramadol due to the risk of serotonin syndrome.
  • P450 Enzyme Interactions: Drugs like chlorphenamine, cimetidine, and diazepam can alter amitriptyline metabolism, leading to toxicity or reduced efficacy.
  • Anticholinergic Effects: Use cautiously with anticholinergic agents (e.g., atropine) to avoid additive effects like constipation and urinary retention.
• Monitoring:
  • Baseline thyroid tests (T3, T4, and free T4) are recommended before therapy, as amitriptyline can lower thyroid hormone levels.
  • Perform regular bloodwork and ECG monitoring for prolonged PR intervals or QTc changes.
• Client Education:
  • The medication requires consistent dosing and may take 2–4 weeks to show full effects.
  • Avoid sudden discontinuation to prevent withdrawal symptoms.
  • Common side effects like sedation and increased appetite should resolve as the animal adjusts to the medication.