AMITRIPTYLINE

(for veterinary information only)

BRAND NAME: ELAVIL

AVAILABLE IN
10 mg, 25 mg, 50 mg,
75 mg, 100 mg AND 150 mg
TABLETS

BACKGROUND

Amitriptyline was developed out of a need in human medicine for anti-anxiety and anti-depressant medications though it has gained some popularity for the treatment of chronic pain syndromes. Amitriptyline is a member of the class of drugs called “tricyclic antidepressants.” It works by increasing the amount of a "happiness" neurotransmitter called "serotonin." This sounds great but there are some side effects that occur as a result of amitriptyline's activity and we will review those later on.

In addition to the neurotransmitter effects, amitriptyline is also a strong antihistamine. Some of its desired effects may be achieved by way of its antihistamine effects in addition to its brain effects.

HOW THIS DRUG IS USED

With amitriptyline becoming widely used in human mental illness, it was not long before small animal uses for this medication came to light. Amitriptyline has been used in animals for separation anxiety, for inappropriate urination in cats, for feline lower urinary tract disease in cats, and for obsessive grooming behaviors in both dogs and cats. In many of these conditions it is not clear which of the above described mechanisms of action are responsible for the desired effects.

Amitriptyline is usually given once or twice daily and can take a couple of weeks before it is possible to judge its effectiveness. It can be given with or without food. If a dose is accidentally skipped, give it when it remembered and adjust the timing of the next dose accordingly. Do not double up on the next dose. Tablets should be stored at room temperature.

SIDE EFFECTS

By blocking amine pumps in the brain, amtriptyline hampers the removal of serotonin so any serotonin you have lasts longer. The problem is that blocking amine pumps in the brain also hampers the removal of norepinephrine which is a fight or flight neurotransmitter. Having more stimulation of "fight or flight" creates what are called "anticholinergic" effects which include: dry mouth, urinary retention, constipation, dried respiratory secretions. Such anticholinergic effects are relatively common amitriptyline side effects.

That said, the most common side effect of amitriptylline is drowsiness/sedation (caused by the increased serotonin).

Anticholinergic side effects would probably not be surprising: dry mouth (manifested in animals often as frequently licking of the lips), urinary retention, constipation.

Tricyclic antidepressants can alter blood sugar levels and falsely lower thyroid testing.

More serious (though rare) potential side effects can include seizures, heart arrhythmia, and/or abnormal bleeding.

INTERACTIONS WITH OTHER MEDICATIONS

Tricyclic antidepressants such as amitriptyline cannot be safely used with monoamine oxidase inhibitors such as Deprenyl (Anipryl^®) or with tramadol, a pain reliever.

The use of cimetadine (Tagamet^®) can interfere with the desired effect of amitriptyline.

Amitriptyline is best not used in conjunction with other drugs with anticholinergic effects, drugs that stimulate the sympathetic nervous system, or with other psychoactive drugs.

Use of the intestinal motility modifier cisapride leads to heart rhythm disturbances when it is combined with certain other medications. Amitripyline is one of those medications so these two drugs should not be used together.

Itraconazole and ketoconazole (antifungal agents) can increase blood levels of amitriptyline thus increasing the toxicity potential. Cyproheptadine may decrease amitriptyline levels rendering it ineffective.

Amitriptyline should not be used in dogs that use an amitraz-based tick control product. To see which products contain amitraz, click here.

CONCERNS AND CAUTIONS

Amitriptyline is removed from the body via the liver. Patients with abnormal liver function may have trouble with this medication. Periodic liver enzyme evaluation (blood testing) is a good idea for patients on this medication long term.

Amitriptyline should not be used in pregnancy or lactation, in patients with seizure disorders, patients with "dry eye" ("KCS"), or in patients with cardiac rhythm disturbances.

Diabetic pets should avoid the use of amitriptyline.

IT CAN TAKE UP TO 3 WEEKS TO DETERMINE IF AMITRIPTYLINE IS EFFECTIVE.

Short version (to help us comply with "Lizzie's Law")

Page last updated: 8/11/2025