Basic Information:

Amitriptyline belongs to the class of drugs known as tricyclic antidepressants (TCA). TCAs primarily affect serotonin and norepinephrine receptors, along with other neurotransmitter systems. It possesses various actions, including antihistaminic, anticholinergic, and sedative properties.

Uses in Dogs and Cats:

Cats: Amitriptyline is frequently prescribed for cats exhibiting spraying or inappropriate elimination behaviors. It can also be used to manage social hierarchy-related anxiety. Additionally, it is sometimes employed in treating idiopathic feline urinary tract disease, although its efficacy remains debated.

Dogs: Common applications in dogs include treating separation anxiety, pruritus (itchiness), and neuropathic pain. While clomipramine is preferred for separation anxiety due to its higher specificity for serotonin receptors, amitriptyline's antihistamine properties make it suitable as an adjunctive treatment for pruritic dogs. Some literature also suggests its use in dogs with osteoarthritis.

Side Effects:

Common: Sedation, constipation, urinary retention. Less common: Hyperexcitability, aggression, cardiac arrhythmias, gastrointestinal disturbances, ataxia (loss of coordination), and disorientation.

Precautions:

Full therapeutic effect may take 7-10 days. Anticipate sedation due to antihistaminic effects. May lower the seizure threshold. Avoid use during pregnancy unless the benefits outweigh the risks. Caution in animals with certain conditions like diabetes, liver or kidney disease, glaucoma, and cardiac arrhythmias.

Drug Interactions:

Potential interactions with monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, sympathomimetic drugs, cisapride, thyroid medications, anticholinergic drugs, CNS depressants, cimetidine, and diazepam.

Overdose:

Overdose can lead to severe cardiac arrhythmias and cardio-respiratory collapse. Prompt recognition is crucial, and gut-emptying protocols may be necessary if identified early.