Amitriptyline is one of the most widely used tricyclic antidepressants (TCAs) in companion animal behavioral medicine, exerting antihistaminic, anti-inflammatory, analgesic, and antidepressant effects. It increases synaptic activity of serotonin and norepinephrine, has significant central and peripheral anticholinergic activity, and stimulates β-adrenergic receptors in smooth muscle (e.g. the bladder), causing a decrease in smooth muscle excitability and a subsequent increase in bladder capacity and storage. Therefore, in felines it is extremely useful in the symptomatic treatment of interstitial cystitis or chronic feline idiopathic lower urinary tract disease, the reduction of pain, inflammation, and inappropriate elimination such as spraying and marking. In canines, Amitriptyline has shown efficacy in reducing anxiety, aggression, depression, and separation anxiety. Amitriptyline is quickly absorbed from the GI tract but can also be applied transdermal in hard to dose patients or in patients where GI upset occurs, despite one study showing minimal absorption.2 It is contraindicated in animals with known hypersensitivity to TCA’s, glaucoma, cardiac disease, renal or hepatic dysfunction. Common side effects seen with Amitriptyline are GI upset, sedation, weight gain, urine retention, mydriasis, neutropenia, and thrombocytopenia. Although Amitriptyline has been used successfully to treat behavior related and urinary tract disorders in cats and dogs, currently it is not approved for veterinary use and is not available as a veterinary preparation.
Suggested Dosing for Cats/Dogs: 5-10mg PO or Topically once daily or
0.5-2mg/kg PO or Topically every 12 to 24 hours
1. Compendium 23(5) May 2001: 433-7
2. Mealey KL, Peck KE, Bennett BS, et al. Systemic absorption of amitriptyline and buspirone after oral and transdermal administration to healthy cats. J Vet Intern Med. 2004; 18(1):43–46.