By Kayla Hyland, DVM; Rania Gollakner, BS, DVM, MPH

What is amitriptyline?

Amitriptyline (brand names: Elavil®, Levate®) is a tricyclic antidepressant used to treat behavior disorders in small animals, such as generalized anxiety and separation anxiety in dogs, and excessive grooming, urine spraying, lower urinary tract disease, pica, and anxiety in cats. It has also been used for nerve pain and itchiness in small animals, and for lower urinary tract disease (FLUTD) in cats. In birds, amitriptyline has been used for behavior problems such as feather picking.

Its use in cats and dogs to treat behavior and other conditions is “off label” or “extra-label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully. as their directions may be significantly different from those on the label.

How is amitriptyline given?

Amitriptyline is given by mouth in the form of a tablet and may be given with or without food. If vomiting occurs when given on an empty stomach, try giving future doses with food or a treat. Amitriptyline may also be specially compounded into a liquid form; make sure to follow the use and storage recommendations on the label.

This medication can take a few weeks before full effects are noted, but side effects can occur immediately. Gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss giving your pet a dose, give the next dose as soon as you remember. However, if it is closer than 12 hours before the next scheduled dose, either:

  1. skip the dose you missed, give it at the next scheduled time, and continue with the regular dosing schedule, or
  2. give the missed dose and then wait the recommended interval before giving the next dose (continue giving it regularly at that new time).

Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Drowsiness/sedation, constipation, dry mouth, and urinary retention are the most common side effects. Less commonly, dogs may exhibit hyperexcitability, irregular heart rhythms, and rarely may develop seizures. Other side effects can occur, such as decreased blood cell counts, vomiting, diarrhea, or endocrine problems (hormonal imbalances).

Side effects in cats may include sedation, increased salivation, urinary retention, anorexia, vomiting, incoordination, disorientation, unkempt hair coat, or heart arrhythmias. Bloodwork may show decreased platelets or white blood cells.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Amitriptyline should not be used if there is a history of sensitivity to other tricyclic antidepressants or diagnosis of hyperthyroidism. It should be used with extreme caution in pets with seizure disorders. Amitriptyline should be used with caution in pets with thyroid disease, urinary retention, liver disorders, dry eye (keratoconjunctivitis sicca), glaucoma, heart arrhythmias, diabetes, or adrenal gland tumors.

There are also many potential drug interactions, but monoamine oxidase inhibitors (MOIs) or flea collars should not be used while your pet is taking amitriptyline.

Amitriptyline’s use in pregnant or lactating animals is not recommended unless the benefits unquestionably outweigh the risks. It should be used with caution in very young or geriatric/elderly pets.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with amitriptyline: acetazolamide/dichlorphenamide, alpha-2 adrenergic agonists, amantadine, ammonium chloride, anesthetic agents, antiarrhythmics, anticholinergic agents, antihypertensive agents, anthracyclines, apomorphine, azole antifungals, barbiturates, benzodiazepines, beta-2 agonists, bethanechol, bromocriptine, buspirone, carbamazepine, cetirizine, cimetidine, cisapride, clonidine, cyproheptadine, desmopressin, diazoxide, divalproex, dobutamine/dopamine/ephedrine, epinephrine, norepinephrine, domperidone, estrogens, fluoroquinolones, hydroxychloroquine, ifosfamide, iohexol, leuprolide, levetiracetam, lithium, macrolides, methylphenidate, metoclopramide, metronidazole, monoamine oxidase inhibitors, muscle relaxants, nitroglycerine/nitroprusside/phenoxybenzamine/tamsulosin, non-DHP calcium channel blockers, NSAIDs, octreotide, opioids, pergolide, phenothiazines, phenytoin, physostigmine, potassium chloride, pregabalin, primidone/phenobarbital, rifampin, rufinamide, selective-serotonin reuptake inhibitors, serotonin receptor antagonists, sulfamethoxazole/trimethoprim, sulfonylureas, sympathomimetic agents, terbinafine, thyroid agents, tramadol, trazodone, valproic acid, vasopressin, warfarin, yohimbine, and zonisamide.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Before starting the medication, your veterinarian may check heart function, a complete blood count, and general bloodwork. During therapy, your veterinarian may check an ECG, blood sugar levels, or monitor your pet to be sure that the medication is working.

How do I store amitriptyline?

Amitriptyline should be stored at room temperature, away from direct sunlight.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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